Description: remove f-strings that require Python 3.6 (https://docs.python.org/3/whatsnew/3.6.html#whatsnew36-pep498)
Author: Olivier Tilloy <olivier.tilloy@canonical.com>

--- a/third_party/python/glean_parser/glean_parser/lint.py
+++ b/third_party/python/glean_parser/glean_parser/lint.py
@@ -42,10 +42,10 @@ def _english_list(items: List[str]) -> s
     if len(items) == 0:
         return ""
     elif len(items) == 1:
-        return f"'{items[0]}'"
+        return "'{}'".format(items[0])
     else:
         return "{}, or '{}'".format(
-            ", ".join([f"'{x}'" for x in items[:-1]]), items[-1]
+            ", ".join(["'{}'".format(x) for x in items[:-1]]), items[-1]
         )
 
 
@@ -88,10 +88,11 @@ def check_common_prefix(
     if i > 0:
         common_prefix = "_".join(first[:i])
         yield (
-            f"Within category '{category_name}', all metrics begin with "
-            f"prefix '{common_prefix}'."
+            "Within category '{}', all metrics begin with "
+            "prefix '{}'."
             "Remove the prefixes on the metric names and (possibly) "
             "rename the category."
+            .format(category_name, common_prefix)
         )
 
 
@@ -131,17 +132,19 @@ def check_unit_in_name(
             or unit_in_name == time_unit.name
         ):
             yield (
-                f"Suffix '{unit_in_name}' is redundant with time_unit "
-                f"'{time_unit.name}'. Only include time_unit."
+                "Suffix '{}' is redundant with time_unit "
+                "'{}'. Only include time_unit."
+                .format(unit_in_name, time_unit.name)
             )
         elif (
             unit_in_name in TIME_UNIT_ABBREV.keys()
             or unit_in_name in TIME_UNIT_ABBREV.values()
         ):
             yield (
-                f"Suffix '{unit_in_name}' doesn't match time_unit "
-                f"'{time_unit.name}'. "
+                "Suffix '{}' doesn't match time_unit "
+                "'{}'. "
                 "Confirm the unit is correct and only include time_unit."
+                .format(unit_in_name, time_unit.name)
             )
 
     elif memory_unit is not None:
@@ -150,26 +153,29 @@ def check_unit_in_name(
             or unit_in_name == memory_unit.name
         ):
             yield (
-                f"Suffix '{unit_in_name}' is redundant with memory_unit "
-                f"'{memory_unit.name}'. "
+                "Suffix '{}' is redundant with memory_unit "
+                "'{}'. "
                 "Only include memory_unit."
+                .format(unit_in_name, memory_unit.name)
             )
         elif (
             unit_in_name in MEMORY_UNIT_ABBREV.keys()
             or unit_in_name in MEMORY_UNIT_ABBREV.values()
         ):
             yield (
-                f"Suffix '{unit_in_name}' doesn't match memory_unit "
-                f"{memory_unit.name}'. "
+                "Suffix '{}' doesn't match memory_unit "
+                "{}'. "
                 "Confirm the unit is correct and only include memory_unit."
+                .format(unit_in_name, memory_unit.name)
             )
 
     elif unit is not None:
         if unit_in_name == unit:
             yield (
-                f"Suffix '{unit_in_name}' is redundant with unit param "
-                f"'{unit}'. "
+                "Suffix '{}' is redundant with unit param "
+                "'{}'. "
                 "Only include unit."
+                .format(unit_in_name, unit)
             )
 
 
@@ -183,8 +189,9 @@ def check_category_generic(
 
     if category_name in GENERIC_CATEGORIES:
         yield (
-            f"Category '{category_name}' is too generic. "
-            f"Don't use {_english_list(GENERIC_CATEGORIES)} for category names"
+            "Category '{}' is too generic. "
+            "Don't use {} for category names"
+            .format(category_name, _english_list(GENERIC_CATEGORIES))
         )
 
 
@@ -195,9 +202,10 @@ def check_bug_number(
 
     if len(number_bugs):
         yield (
-            f"For bugs {', '.join(number_bugs)}: "
+            "For bugs {}: "
             "Bug numbers are deprecated and should be changed to full URLs. "
             "For example, use 'http://bugzilla.mozilla.org/12345' instead of '12345'."
+            .format(', '.join(number_bugs))
         )
 
 
@@ -220,7 +228,7 @@ def check_misspelled_pings(
         for builtin in pings.RESERVED_PING_NAMES:
             distance = _hamming_distance(ping, builtin)
             if distance == 1:
-                yield f"Ping '{ping}' seems misspelled. Did you mean '{builtin}'?"
+                yield "Ping '{}' seems misspelled. Did you mean '{}'?".format(ping, builtin)
 
 
 def check_user_lifetime_expiration(
@@ -281,8 +289,9 @@ class GlinterNit:
 
     def format(self):
         return (
-            f"{self.check_type.name.upper()}: {self.check_name}: "
-            f"{self.name}: {self.msg}"
+            "{}: {}: "
+            "{}: {}"
+            .format(self.check_type.name.upper(), self.check_name, self.name, self.msg)
         )
 
 
@@ -374,7 +383,7 @@ def lint_yaml_files(input_filepaths: Ite
     if len(nits):
         print("Sorry, Glean found some glinter nits:", file=file)
         for (path, p) in nits:
-            print(f"{path} ({p.line}:{p.column}) - {p.message}")
+            print("{} ({}:{}) - {}".format(path, p.line, p.column, p.message))
         print("", file=file)
         print("Please fix the above nits to continue.", file=file)
 
--- a/third_party/python/glean_parser/glean_parser/markdown.py
+++ b/third_party/python/glean_parser/glean_parser/markdown.py
@@ -73,7 +73,7 @@ def metrics_docs(obj_name: str) -> str:
     if obj_name.startswith("labeled_"):
         fixedup_name += "s"
 
-    return f"https://mozilla.github.io/glean/book/user/metrics/{fixedup_name}.html"
+    return "https://mozilla.github.io/glean/book/user/metrics/{}.html".format(fixedup_name)
 
 
 def ping_docs(ping_name: str) -> str:
@@ -84,7 +84,7 @@ def ping_docs(ping_name: str) -> str:
     if ping_name not in pings.RESERVED_PING_NAMES:
         return ""
 
-    return f"https://mozilla.github.io/glean/book/user/pings/{ping_name}.html"
+    return "https://mozilla.github.io/glean/book/user/pings/{}.html".format(ping_name)
 
 
 def if_empty(
--- a/third_party/python/glean_parser/glean_parser/parser.py
+++ b/third_party/python/glean_parser/glean_parser/parser.py
@@ -46,7 +46,8 @@ def _update_validator(validator):
         if len(missing_properties):
             missing_properties = sorted(list(missing_properties))
             yield ValidationError(
-                f"Missing required properties: {', '.join(missing_properties)}"
+                "Missing required properties: {}"
+                .format(', '.join(missing_properties))
             )
 
     validator.VALIDATORS["required"] = required
@@ -65,7 +66,7 @@ def _load_file(
         return {}, None
 
     if content is None:
-        yield util.format_error(filepath, "", f"'{filepath}' file can not be empty.")
+        yield util.format_error(filepath, "", "'{}' file can not be empty.".format(filepath))
         return {}, None
 
     if not isinstance(content, dict):
@@ -76,7 +77,7 @@ def _load_file(
 
     schema_key = content.get("$schema")
     if not isinstance(schema_key, str):
-        raise TypeError(f"Invalid schema key {schema_key}")
+        raise TypeError("Invalid schema key {}".format(schema_key))
 
     filetype = FILE_TYPES.get(schema_key)
 
@@ -117,7 +118,7 @@ def _get_schema(
             util.format_error(
                 filepath,
                 "",
-                f"$schema key must be one of {', '.join(schemas.keys())}",
+                "$schema key must be one of {}".format(', '.join(schemas.keys())),
             )
         )
     return schemas[schema_id]
@@ -189,7 +190,7 @@ def _instantiate_metrics(
         if not config.get("allow_reserved") and category_key.split(".")[0] == "glean":
             yield util.format_error(
                 filepath,
-                f"For category '{category_key}'",
+                "For category '{}'".format(category_key),
                 "Categories beginning with 'glean' are reserved for "
                 "Glean internal use.",
             )
@@ -197,7 +198,7 @@ def _instantiate_metrics(
         all_objects.setdefault(category_key, OrderedDict())
 
         if not isinstance(category_val, dict):
-            raise TypeError(f"Invalid content for {category_key}")
+            raise TypeError("Invalid content for {}".format(category_key))
 
         for metric_key, metric_val in category_val.items():
             try:
@@ -207,7 +208,7 @@ def _instantiate_metrics(
             except Exception as e:
                 yield util.format_error(
                     filepath,
-                    f"On instance {category_key}.{metric_key}",
+                    "On instance {}.{}".format(category_key, metric_key),
                     str(e),
                 )
                 metric_obj = None
@@ -218,7 +219,7 @@ def _instantiate_metrics(
                 ):
                     yield util.format_error(
                         filepath,
-                        f"On instance {category_key}.{metric_key}",
+                        "On instance {}.{}".format(category_key, metric_key),
                         'Only internal metrics may specify "all-pings" '
                         'in "send_in_pings"',
                     )
@@ -234,8 +235,9 @@ def _instantiate_metrics(
                     filepath,
                     "",
                     (
-                        f"Duplicate metric name '{category_key}.{metric_key}' "
-                        f"already defined in '{already_seen}'"
+                        "Duplicate metric name '{}.{}' "
+                        "already defined in '{}'"
+                        .format(category_key, metric_key, already_seen)
                     ),
                 )
             else:
@@ -261,17 +263,17 @@ def _instantiate_pings(
             if ping_key in RESERVED_PING_NAMES:
                 yield util.format_error(
                     filepath,
-                    f"For ping '{ping_key}'",
-                    f"Ping uses a reserved name ({RESERVED_PING_NAMES})",
+                    "For ping '{}'".format(ping_key),
+                    "Ping uses a reserved name ({})".format(RESERVED_PING_NAMES),
                 )
                 continue
         if not isinstance(ping_val, dict):
-            raise TypeError(f"Invalid content for ping {ping_key}")
+            raise TypeError("Invalid content for ping {}".format(ping_key))
         ping_val["name"] = ping_key
         try:
             ping_obj = Ping(**ping_val)
         except Exception as e:
-            yield util.format_error(filepath, f"On instance '{ping_key}'", str(e))
+            yield util.format_error(filepath, "On instance '{}'".format(ping_key), str(e))
             continue
 
         already_seen = sources.get(ping_key)
@@ -280,8 +282,9 @@ def _instantiate_pings(
             yield util.format_error(
                 filepath,
                 "",
-                f"Duplicate ping name '{ping_key}' "
-                f"already defined in '{already_seen}'",
+                "Duplicate ping name '{}' "
+                "already defined in '{}'"
+                .format(ping_key, already_seen),
             )
         else:
             all_objects.setdefault("pings", {})[ping_key] = ping_obj
--- a/third_party/python/glean_parser/glean_parser/util.py
+++ b/third_party/python/glean_parser/glean_parser/util.py
@@ -132,7 +132,7 @@ def load_yaml_or_json(path: Path, ordere
             else:
                 return yaml.load(fd, Loader=_NoDatesSafeLoader)
     else:
-        raise ValueError(f"Unknown file extension {path.suffix}")
+        raise ValueError("Unknown file extension {}".format(path.suffix))
 
 
 def ensure_list(value: Any) -> Sequence[Any]:
@@ -331,9 +331,9 @@ def format_error(filepath: Union[str, Pa
     else:
         filepath = "<string>"
     if header:
-        return f"{filepath}: {header}\n{_utils.indent(content)}"
+        return "{}: {}\n{}".format(filepath, header, _utils.indent(content))
     else:
-        return f"{filepath}:\n{_utils.indent(content)}"
+        return "{}:\n{}".format(filepath, _utils.indent(content))
 
 
 def parse_expires(expires: str) -> datetime.date:
@@ -351,8 +351,8 @@ def parse_expires(expires: str) -> datet
             return datetime.date.fromisoformat(expires)
     except ValueError:
         raise ValueError(
-            f"Invalid expiration date '{expires}'. "
-            "Must be of the form yyyy-mm-dd in UTC."
+            "Invalid expiration date '{}'. "
+            "Must be of the form yyyy-mm-dd in UTC.".format(expires)
         )
 
 
@@ -382,7 +382,7 @@ def validate_expires(expires: str) -> No
     max_date = datetime.datetime.now() + datetime.timedelta(days=730)
     if date > max_date.date():
         raise ValueError(
-            f"'{expires}' is more than 730 days (~2 years) in the future.",
+            "'{}' is more than 730 days (~2 years) in the future.".format(expires),
             "Please make sure this is intentional.",
             "You can supress this warning by adding EXPIRATION_DATE_TOO_FAR to no_lint",
             "See: https://mozilla.github.io/glean_parser/metrics-yaml.html#no_lint",
--- a/third_party/python/glean_parser/tools/extract_data_categories.py
+++ b/third_party/python/glean_parser/tools/extract_data_categories.py
@@ -62,7 +62,7 @@ def fetch_url(url: str) -> str:
     if content is not None:
         return content
 
-    print(f"Fetching {url}")
+    print("Fetching {}".format(url))
     content = urlopen(url).read()
     cache[url] = content
     time.sleep(0.5)
@@ -97,7 +97,7 @@ def categories_as_strings(categories: Se
     """
     if len(categories):
         return [
-            CATEGORY_MAP.get(x, f"!!!UNKNOWN CATEGORY {x}")
+            CATEGORY_MAP.get(x, "!!!UNKNOWN CATEGORY {}".format(x))
             for x in sorted(list(categories))
         ]
     else:
@@ -119,24 +119,24 @@ def update_lines(
 
     for line in lines_iter:
         output.append(line)
-        if line.startswith(f"{category_name}:"):
+        if line.startswith("{}:".format(category_name)):
             break
 
     for line in lines_iter:
         output.append(line)
-        if line.startswith(f"  {metric_name}:"):
+        if line.startswith("  {}:".format(metric_name)):
             break
 
     for line in lines_iter:
         output.append(line)
-        if line.startswith(f"    data_reviews:"):
+        if line.startswith("    data_reviews:"):
             break
 
     for line in lines_iter:
         if not line.strip().startswith("- "):
             output.append("    data_sensitivity:\n")
             for data_sensitivity in data_sensitivity_values:
-                output.append(f"      - {data_sensitivity}\n")
+                output.append("      - {}\n".format(data_sensitivity))
             output.append(line)
             break
         else:
--- a/third_party/python/glean_parser/glean_parser/metrics.py
+++ b/third_party/python/glean_parser/glean_parser/metrics.py
@@ -138,7 +138,7 @@ class Metric:
 
         metric_type = metric_info["type"]
         if not isinstance(metric_type, str):
-            raise TypeError(f"Unknown metric type {metric_type}")
+            raise TypeError("Unknown metric type {}".format(metric_type))
         return cls.metric_types[metric_type](
             category=category,
             name=name,
--- a/third_party/python/glean_parser/glean_parser/translate.py
+++ b/third_party/python/glean_parser/glean_parser/translate.py
@@ -112,7 +112,7 @@ def translate_metrics(
                 for filepath in output_dir.glob(clear_pattern):
                     filepath.unlink()
             if len(list(output_dir.iterdir())):
-                print(f"Extra contents found in '{output_dir}'.")
+                print("Extra contents found in '{}'.".format(output_dir))
 
         # We can't use shutil.copytree alone if the directory already exists.
         # However, if it doesn't exist, make sure to create one otherwise
@@ -146,7 +146,7 @@ def translate(
     format_desc = OUTPUTTERS.get(output_format, None)
 
     if format_desc is None:
-        raise ValueError(f"Unknown output format '{output_format}'")
+        raise ValueError("Unknown output format '{}'".format(output_format))
 
     return translate_metrics(
         input_filepaths,
--- a/toolkit/components/glean/build_scripts/glean_parser_ext/js.py	Tue Nov 17 21:27:44 2020 +0000
+++ b/toolkit/components/glean/build_scripts/glean_parser_ext/js.py	Wed Nov 18 10:51:04 2020 +0100
@@ -57,7 +57,7 @@
     """
     The metric's unique identifier, including the category and name
     """
-    return f"{category}.{metric_name}"
+    return "{}.{}".format(category, metric_name)
 
 
 def type_name(type):
--- a/toolkit/components/glean/build_scripts/glean_parser_ext/rust.py	Tue Nov 17 21:27:44 2020 +0000
+++ b/toolkit/components/glean/build_scripts/glean_parser_ext/rust.py	Wed Nov 18 10:51:04 2020 +0100
@@ -175,7 +175,7 @@
 
                 metric_name = util.snake_case(metric.name)
                 category_name = util.snake_case(category_name)
-                full_path = f"{category_name}::{metric_name}"
+                full_path = "{}::{}".format(category_name, metric_name)
                 objs_by_type[key].append((get_metric_id(metric), full_path))
 
     # Now for the modules for each category.