Test that extra prefix "WARNING:" is omitted

This changes test_initial_refresh_from_bad_git_path_env_warn to
assert a message with no added "WARNING:" prefix. As discussed
in gitpython-developers#1815, the extra prefix is confusing with logging configured,
showing "CRITICAL:git.cmd:WARNING: Bad git executable." instead of
"CRITICAL:git.cmd: Bad git executable."

Author: EliahKagan

test/test_git.py

@@ -363,7 +363,7 @@ def test_initial_refresh_from_bad_git_path_env_warn(self, case):
                     refresh()
                 self.assertEqual(len(ctx.records), 1)
                 message = ctx.records[0].getMessage()
-                self.assertRegex(message, r"\AWARNING: Bad git executable.\n")
+                self.assertRegex(message, r"\ABad git executable.\n")
                 self.assertEqual(self.git.GIT_PYTHON_GIT_EXECUTABLE, "git")
 
     @ddt.data(("2",), ("r",), ("raise",), ("e",), ("error",))