Add unit test for issue #996

.gitignore

@@ -1,5 +1,6 @@
 /.cache/
 /.eggs/
+/.envrc
 /.tox/
 /build/
 /dist/

Makefile

@@ -1,4 +1,4 @@
-.PHONY: build
+.PHONY: build html
 
 build:
 	python setup.py build_ext --inplace -g

pygit2/errors.py

@@ -34,6 +34,10 @@ def check_error(err, io=False):
     if err >= 0:
         return
 
+    # These are special error codes, they should never reach here
+    test = err != C.GIT_EUSER and err != C.GIT_PASSTHROUGH
+    assert test, f'Unexpected error code {err}'
+
     # Error message
     giterr = C.git_error_last()
     if giterr != ffi.NULL:

test/test_repository.py

@@ -643,6 +643,17 @@ def test_clone_with_credentials(self):
 
         assert not repo.is_empty
 
+    @unittest.skipIf(utils.no_network(), "Requires network")
+    def test_clone_bad_credentials(self):
+        class MyCallbacks(pygit2.RemoteCallbacks):
+            def credentials(self, url, username, allowed):
+                raise RuntimeError('Unexpected error')
+
+        url = "https://github.com/github/github"
+        with pytest.raises(RuntimeError) as exc:
+            clone_repository(url, self._temp_dir, callbacks=MyCallbacks())
+        assert str(exc.value) == 'Unexpected error'
+
     def test_clone_with_checkout_branch(self):
         # create a test case which isolates the remote
         test_repo = clone_repository('./test/data/testrepo.git',