loader: Ensure to search in a string when processing GitProtocolError

First argument of the exception is not always a string so force its text
representation before searching in it.

swh/loader/git/loader.py

@@ -329,7 +329,7 @@ class GitLoader(BaseGitLoader):
                 " not found",
                 "unexpected http resp 401",
             ]:
-                if msg in e.args[0]:
+                if msg in str(e.args[0]):
                     raise NotFound(e)
             # otherwise transmit the error
             raise

swh/loader/git/tests/test_loader.py

@@ -73,11 +73,12 @@ class CommonGitLoaderNotFound:
     @pytest.mark.parametrize(
         "failure_exception",
         [
-            IOError,
-            ObjectFormatException,
-            OSError,
-            ValueError,
-            GitProtocolError,
+            IOError("failure"),
+            ObjectFormatException("failure"),
+            OSError("failure"),
+            ValueError("failure"),
+            GitProtocolError("failure"),
+            GitProtocolError(ConnectionResetError("Connection reset by peer")),
         ],
     )
     def test_load_visit_failure(self, failure_exception):
@@ -88,7 +89,7 @@ class CommonGitLoaderNotFound:
             "swh.loader.git.loader.GitLoader.fetch_pack_from_origin"
         )
 
-        mock.side_effect = failure_exception("failure")
+        mock.side_effect = failure_exception
 
         res = self.loader.load()
         assert res == {"status": "failed"}