Add pylint false positive to list of pylint false positives.

This is another false positive resulting from pylint's inability to find
GLib in gi.repository.

Signed-off-by: mulhern <amulhern@redhat.com>

tests/pylint/pylint-false-positives

@@ -1,4 +1,5 @@
 ^blivet/.*: \[E0611\(no\-name\-in\-module\).*\] No name 'GLib' in module 'gi.repository'$
+^blivet/.*: \[E0712\(catching\-non\-exception\).*\] Catching an exception which doesn't inherit from BaseException: GError$
 ^blivet/__init__.py:[[:digit:]]+: \[W0602\(global\-variable\-not\-assigned\), enable_installer_mode\] Using global for 'BootLoaderError' but no assignment is done$
 ^blivet/__init__.py:[[:digit:]]+: \[W0602\(global\-variable\-not\-assigned\), enable_installer_mode\] Using global for 'ERROR_RAISE' but no assignment is done$
 ^blivet/__init__.py:[[:digit:]]+: \[W0602\(global\-variable\-not\-assigned\), enable_installer_mode\] Using global for 'ROOT_PATH' but no assignment is done$