[PATCH v2 09/12] python: update mkvenv to type-check under different python versions

[John Snow <jsnow@redhat.com>]

Currently, we instruct mypy to pretend it is type checking under a
specific version of python. For our case, where our scripts may in fact
actually be executing under a number of different environments in the
build system, we want mypy to remove this restriction.

This patch adjusts some of the import logic in mkvenv.py to make it type
check under a wider range of python versions. It's largely arbitrary, to
work around some mypy fussiness.

Signed-off-by: John Snow <jsnow@redhat.com>
---
 python/scripts/mkvenv.py | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/python/scripts/mkvenv.py b/python/scripts/mkvenv.py
index 8026ca24861..b5d1edd3afa 100644
--- a/python/scripts/mkvenv.py
+++ b/python/scripts/mkvenv.py
@@ -99,16 +99,18 @@
         HAVE_DISTLIB = False
 
 # Try to load tomllib, with a fallback to tomli.
-# HAVE_TOMLLIB is checked below, just-in-time, so that mkvenv does not fail
+# TOML is checked below, just-in-time, so that mkvenv does not fail
 # outside the venv or before a potential call to ensurepip in checkpip().
-HAVE_TOMLLIB = True
+TOML = None
 try:
     import tomllib
+    TOML = tomllib
 except ImportError:
     try:
-        import tomli as tomllib
+        import tomli
+        TOML = tomli
     except ImportError:
-        HAVE_TOMLLIB = False
+        pass
 
 # Do not add any mandatory dependencies from outside the stdlib:
 # This script *must* be usable standalone!
@@ -194,6 +196,7 @@ def compute_venv_libpath(context: SimpleNamespace) -> str:
         # Python 3.12+, not strictly necessary because it's documented
         # to be the same as 3.10 code below:
         if sys.version_info >= (3, 12):
+            assert isinstance(context.lib_path, str)
             return context.lib_path
 
         # Python 3.10+
@@ -710,7 +713,7 @@ def _do_ensure(
 
 
 def _parse_groups(file: str) -> dict[str, dict[str, Any]]:
-    if not HAVE_TOMLLIB:
+    if not TOML:
         if sys.version_info < (3, 11):
             raise Ouch("found no usable tomli, please install it")
 
@@ -722,7 +725,7 @@ def _parse_groups(file: str) -> dict[str, dict[str, Any]]:
     # Debian bullseye-backports) and v2.0.x
     with open(file, encoding="ascii") as depfile:
         contents = depfile.read()
-        return tomllib.loads(contents)  # type: ignore
+        return TOML.loads(contents)  # type: ignore
 
 
 def ensure_group(
-- 
2.48.1