properly detect python3-gi

debian/changelog

+matplotlib (3.10.1+dfsg1-3) unstable; urgency=medium
+
+  [ James Addison ]
+  * Properly detect python3-gi absence/presence (Closes: #1101565)
+
+ -- Alexandre Detiste <tchet@debian.org>  Sat, 19 Apr 2025 17:28:04 +0200
+
 matplotlib (3.10.1+dfsg1-2) unstable; urgency=medium
 
   * Release to unstable

debian/patches/fix-gi-import-empty-module.patch

+From: James Addison <jay@jp-hosting.net>
+Date: Tue, 01 Apr 2025 09:17:28 +0000
+Subject: Raise import error if PyGObject module is empty
+ .
+ When GI overrides are installed, the dist-packages/gi directory is
+ non-empty, and this allows Python3 to import the module.  This can
+ happen when Debian packages other than python3-gi are installed.
+ .
+ Detect an empty __file__ attribute on the imported module to check
+ whether it is genuinely the expected GObject Python module.
+ .
+ Credit to Francesco Ballarin for the test condition in #1101565.
+
+Bug: http://bugs.debian.org/1101565
+---
+--- a/lib/matplotlib/backends/backend_gtk3.py
++++ b/lib/matplotlib/backends/backend_gtk3.py
+@@ -11,6 +11,9 @@
+ 
+ try:
+     import gi
++
++    if gi.__file__ is None:
++        raise ImportError("Error: PyGObject module is empty")
+ except ImportError as err:
+     raise ImportError("The GTK3 backends require PyGObject") from err
+ 
+--- a/lib/matplotlib/backends/backend_gtk4.py
++++ b/lib/matplotlib/backends/backend_gtk4.py
+@@ -10,6 +10,9 @@
+ 
+ try:
+     import gi
++
++    if gi.__file__ is None:
++        raise ImportError("Error: PyGObject module is empty")
+ except ImportError as err:
+     raise ImportError("The GTK4 backends require PyGObject") from err
+ 

debian/patches/series

@@ -11,3 +11,4 @@ fix-test_compressed_suptitle.patch
 drop-sphinx-unpackaged-exts.patch
 do-not-install-pfb.patch
 fix-auto-backend-case-sensitivity.patch
+fix-gi-import-empty-module.patch