tests: fix code for tests with python 3.7 (#3335)

Author: Panaetius

renku/infrastructure/repository.py

@@ -35,7 +35,6 @@
     Dict,
     Generator,
     List,
-    Literal,
     NamedTuple,
     Optional,
     Sequence,
@@ -53,6 +52,11 @@
 from renku.core import errors
 from renku.core.util.os import delete_dataset_file, get_absolute_path
 
+try:
+    from typing_extensions import Literal  # NOTE: Required for Python 3.7 compatibility
+except ImportError:
+    from typing import Literal  # type: ignore
+
 NULL_TREE = git.NULL_TREE
 _MARKER = object()
 GIT_IGNORE = ".gitignore"