[PATCH 1/3] python/mkvenv: ensure HAVE_LIB variables are actually constants

[John Snow <jsnow@redhat.com>]

Pylint 4.x has refined checking for variable names that behave as
constants vs ones that do not; unfortunately our tricky import machinery
is perceived as these variables being re-assigned.

Add a temporary variable with an underscore and assign to the global
constants precisely once to alleviate this new nag message. Add an
ignore for this name for older versions of pylint that developers may
have installed locally.

(In other words: there is no solution that will cater to both pre- and
post- 4.x versions, so we target 4.x here and silence older versions.)

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
---
 python/scripts/mkvenv.py | 24 ++++++++++++++++--------
 python/setup.cfg         |  1 +
 2 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/python/scripts/mkvenv.py b/python/scripts/mkvenv.py
index 9aed266df1b..a064709e6ce 100644
--- a/python/scripts/mkvenv.py
+++ b/python/scripts/mkvenv.py
@@ -92,7 +92,7 @@
 # Try to load distlib, with a fallback to pip's vendored version.
 # HAVE_DISTLIB 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_DISTLIB = True
+_import_ok = True
 try:
     import distlib.scripts
 except ImportError:
@@ -102,11 +102,13 @@
         from pip._vendor import distlib
         import pip._vendor.distlib.scripts  # noqa, pylint: disable=unused-import
     except ImportError:
-        HAVE_DISTLIB = False
+        _import_ok = False
+
+HAVE_DISTLIB = _import_ok
 
 # pip 25.2 does not vendor distlib.version, but it uses vendored
 # packaging.version
-HAVE_DISTLIB_VERSION = True
+_import_ok = True
 try:
     import distlib.version  # pylint: disable=ungrouped-imports
 except ImportError:
@@ -114,9 +116,11 @@
         # pylint: disable=unused-import,ungrouped-imports
         import pip._vendor.distlib.version  # noqa
     except ImportError:
-        HAVE_DISTLIB_VERSION = False
+        _import_ok = False
 
-HAVE_PACKAGING_VERSION = True
+HAVE_DISTLIB_VERSION = _import_ok
+
+_import_ok = True
 try:
     # Do not bother importing non-vendored packaging, because it is not
     # in stdlib.
@@ -125,20 +129,24 @@
     import pip._vendor.packaging.requirements  # noqa
     import pip._vendor.packaging.version  # noqa
 except ImportError:
-    HAVE_PACKAGING_VERSION = False
+    _import_ok = False
+
+HAVE_PACKAGING_VERSION = _import_ok
 
 
 # Try to load tomllib, with a fallback to tomli.
 # HAVE_TOMLLIB 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
+_import_ok = True
 try:
     import tomllib
 except ImportError:
     try:
         import tomli as tomllib
     except ImportError:
-        HAVE_TOMLLIB = False
+        _import_ok = False
+
+HAVE_TOMLLIB = _import_ok
 
 # Do not add any mandatory dependencies from outside the stdlib:
 # This script *must* be usable standalone!
diff --git a/python/setup.cfg b/python/setup.cfg
index d7f5dc7bafe..f40f11396c9 100644
--- a/python/setup.cfg
+++ b/python/setup.cfg
@@ -159,6 +159,7 @@ good-names=i,
            c,   # for c in string: ...
            T,   # for TypeVars. See pylint#3401
            SocketAddrT,  # Not sure why this is invalid.
+           _import_ok,  # For mkvenv import trickery and compatibility pre-4.x
 
 [pylint.similarities]
 # Ignore imports when computing similarities.
-- 
2.51.1