Fix support for pip versions pre-21.3

CHANGELOG.rst

@@ -2,6 +2,10 @@
 Release History
 ---------------
 
+2.3.2
+
+- Fixed support for pip < 21.3
+
 2.3.1
 
 - Fixed `--skip-incompatible` skipping other requirements too.

pip_check_reqs/__init__.py

@@ -1 +1 @@
-__version__ = '2.3.1'
+__version__ = '2.3.2'

pip_check_reqs/common.py

@@ -14,46 +14,50 @@
 except ImportError:  # pragma: no cover
     from pip._internal.download import PipSession
 from pip._internal.req.req_file import parse_requirements
-from pip._internal.utils.compat import stdlib_pkgs
-from pip._internal.metadata import get_default_environment, get_environment
-from pip._internal.metadata.pkg_resources import Distribution as _Dist
-from pip._vendor.pkg_resources import Distribution
+try:
+    from pip._internal.utils.misc import get_installed_distributions
+except ImportError:  # pip>=21.3
+    from pip._internal.utils.compat import stdlib_pkgs
+    from pip._internal.metadata import get_default_environment, get_environment
+    from pip._internal.metadata.pkg_resources import Distribution as _Dist
+    from pip._vendor.pkg_resources import Distribution
+
+    # get_installed_distributions was removed in pip 21.3.
+    # This is a copy from pip.
+    # See
+    # https://github.com/pypa/pip/commit/d051a00fc57037104fca85ad8ebf2cdbd1e32d24#diff-058e40cb3a9ea705f655937e48f3a053f5dc7c500b7f1b2aae76e9bd673faf64.
+    #
+    # This is mocked in all tests (unfortunately) and so we do not cover this
+    # function.
+    def get_installed_distributions(
+         local_only: bool = True,
+         skip: Container[str] = stdlib_pkgs,
+         include_editables: bool = True,
+         editables_only: bool = False,
+         user_only: bool = False,
+         paths: Optional[List[str]] = None,
+     ) -> List[Distribution]:  # pragma: no cover
+        """Return a list of installed Distribution objects.
+
+        Left for compatibility until direct pkg_resources uses are refactored
+        out.
+        """
+        if paths is None:
+            env = get_default_environment()
+        else:
+            env = get_environment(paths)
 
-log = logging.getLogger(__name__)
+        dists = env.iter_installed_distributions(
+            local_only=local_only,
+            skip=skip,
+            include_editables=include_editables,
+            editables_only=editables_only,
+            user_only=user_only,
+        )
+        return [cast(_Dist, dist)._dist for dist in dists]
 
 
-# get_installed_distributions was removed in pip 21.3.
-# This is a copy from pip.
-# See
-# https://github.com/pypa/pip/commit/d051a00fc57037104fca85ad8ebf2cdbd1e32d24#diff-058e40cb3a9ea705f655937e48f3a053f5dc7c500b7f1b2aae76e9bd673faf64.
-#
-# This is mocked in all tests (unfortunately) and so we do not cover this
-# function.
-def get_installed_distributions(
-     local_only: bool = True,
-     skip: Container[str] = stdlib_pkgs,
-     include_editables: bool = True,
-     editables_only: bool = False,
-     user_only: bool = False,
-     paths: Optional[List[str]] = None,
- ) -> List[Distribution]:  # pragma: no cover
-    """Return a list of installed Distribution objects.
-
-    Left for compatibility until direct pkg_resources uses are refactored out.
-    """
-    if paths is None:
-        env = get_default_environment()
-    else:
-        env = get_environment(paths)
-
-    dists = env.iter_installed_distributions(
-        local_only=local_only,
-        skip=skip,
-        include_editables=include_editables,
-        editables_only=editables_only,
-        user_only=user_only,
-    )
-    return [cast(_Dist, dist)._dist for dist in dists]
+log = logging.getLogger(__name__)
 
 
 class FoundModule: