Fetch raw github repository config

Rather than fetching base64-encoded json and decoding it ourselves,
request the raw text of the config file available in the github
repository. This aligns with the approach used in llnl#145.

Author: cmelone

src/hubcast/clients/github/client.py

@@ -1,4 +1,3 @@
-import base64
 import logging
 
 import aiohttp
@@ -10,10 +9,6 @@
 log = logging.getLogger(__name__)
 
 
-class InvalidConfigEncodingError(Exception):
-    pass
-
-
 class InvalidConfigYAMLError(Exception):
     pass
 
@@ -84,13 +79,8 @@ async def get_repo_config(self):
 
             # get the contents of the repository hubcast.yml file
             url = f"/repos/{self.repo_owner}/{self.repo_name}/contents/.github/hubcast.yml"
-            data = await gh.getitem(url)
-
-            # decode returned file
-            if data["encoding"] == "base64":
-                config_str = base64.b64decode(data["content"])
-            else:
-                raise InvalidConfigEncodingError()
+            # get raw contents rather than base64 encoded json
+            config_str = await gh.getitem(url, accept="application/vnd.github.raw+json")
 
             try:
                 config = yaml.safe_load(config_str)