Support Python 3.8-provided importlib.metadata (#482)

The importlib_metadata package is a backport of the importlib.metadata
module from Python 3.8. Fedora (and possibly others) no longer package
importlib_metadata because they ship Python versions which have the
functionality built-in.

Signed-off-by: Scott K Logan <[email protected]>

Author: cottsay

launch/launch/frontend/parser.py

@@ -24,7 +24,10 @@
 from typing import TYPE_CHECKING
 from typing import Union
 
-import importlib_metadata
+try:
+    import importlib.metadata as importlib_metadata
+except ModuleNotFoundError:
+    import importlib_metadata
 
 from .entity import Entity
 from .expose import instantiate_action