Isolate EXTERNALLY-MANAGED parsing logic

This makes the parser easier to test.

Author: uranusjr

src/pip/_internal/exceptions.py

@@ -8,6 +8,7 @@
 import configparser
 import contextlib
 import locale
+import logging
 import re
 import sys
 from itertools import chain, groupby, repeat
@@ -25,6 +26,8 @@
     from pip._internal.metadata import BaseDistribution
     from pip._internal.req.req_install import InstallRequirement
 
+logger = logging.getLogger(__name__)
+
 
 #
 # Scaffolding
@@ -708,10 +711,15 @@ def _iter_externally_managed_error_keys() -> Iterator[str]:
         yield "Error"
 
     @classmethod
-    def from_config(
-        cls,
-        parser: configparser.ConfigParser,
-    ) -> "ExternallyManagedEnvironment":
+    def from_config(cls, config: str) -> "ExternallyManagedEnvironment":
+        parser = configparser.ConfigParser(interpolation=None)
+        try:
+            parser.read(config, encoding="utf-8")
+        except (OSError, UnicodeDecodeError):
+            from pip._internal.utils._log import VERBOSE
+
+            exc_info = logger.isEnabledFor(VERBOSE)
+            logger.warning("Failed to read %s", config, exc_info=exc_info)
         try:
             section = parser["externally-managed"]
         except KeyError:

src/pip/_internal/utils/misc.py

@@ -1,12 +1,12 @@
 # The following comment should be removed at some point in the future.
 # mypy: strict-optional=False
 
-import configparser
 import contextlib
 import errno
 import getpass
 import hashlib
 import io
+import logging
 import os
 import posixpath
 import shutil
@@ -41,7 +41,6 @@
 from pip import __version__
 from pip._internal.exceptions import CommandError, ExternallyManagedEnvironment
 from pip._internal.locations import get_major_minor_version
-from pip._internal.utils._log import VERBOSE, getLogger
 from pip._internal.utils.compat import WINDOWS
 from pip._internal.utils.virtualenv import running_under_virtualenv
 
@@ -63,8 +62,7 @@
     "ConfiguredBuildBackendHookCaller",
 ]
 
-
-logger = getLogger(__name__)
+logger = logging.getLogger(__name__)
 
 T = TypeVar("T")
 ExcInfo = Tuple[Type[BaseException], BaseException, TracebackType]
@@ -592,17 +590,11 @@ def check_externally_managed() -> None:
     raised.
     """
     if running_under_virtualenv():
-        return None
+        return
     marker = os.path.join(sysconfig.get_path("stdlib"), "EXTERNALLY-MANAGED")
     if not os.path.isfile(marker):
         return
-    parser = configparser.ConfigParser(interpolation=None)
-    try:
-        parser.read(marker, encoding="utf-8")
-    except (OSError, UnicodeDecodeError):
-        exc_info = logger.isEnabledFor(VERBOSE)
-        logger.warning("Failed to read %s", marker, exc_info=exc_info)
-    raise ExternallyManagedEnvironment.from_config(parser)
+    raise ExternallyManagedEnvironment.from_config(marker)
 
 
 def is_console_interactive() -> bool: