Retry GitHub download failures (#3729)

* Retry GitHub download failures

* Refactor and add tests

* Fixed linting and added comment

* Fixing unit test assertRaises

Co-authored-by: Kyle Wigley <kyle@fishtownanalytics.com>

* Fixing casing

Co-authored-by: Kyle Wigley <kyle@fishtownanalytics.com>

* Changing to use partial for function calls

Co-authored-by: Kyle Wigley <kyle@fishtownanalytics.com>

automatic commit by git-black, original commits:
  09ea989

core/dbt/clients/registry.py

@@ -43,14 +43,14 @@ def _get(path, registry_base_url=None):
 
 
 def index(registry_base_url=None):
-    return _get_with_retries('api/v1/index.json', registry_base_url)
+    return _get_with_retries("api/v1/index.json", registry_base_url)
 
 
 index_cached = memoized(index)
 
 
 def packages(registry_base_url=None):
-    return _get_with_retries('api/v1/packages.json', registry_base_url)
+    return _get_with_retries("api/v1/packages.json", registry_base_url)
 
 
 def package(name, registry_base_url=None):
@@ -80,7 +80,7 @@ def package(name, registry_base_url=None):
 
 
 def package_version(name, version, registry_base_url=None):
-    return _get_with_retries('api/v1/{}/{}.json'.format(name, version), registry_base_url)
+    return _get_with_retries("api/v1/{}/{}.json".format(name, version), registry_base_url)
 
 
 def get_available_versions(name):

core/dbt/utils.py

@@ -621,7 +621,7 @@ def _connection_exception_retry(fn, max_attempts: int, attempt: int = 0):
             time.sleep(1)
             _connection_exception_retry(fn, max_attempts, attempt + 1)
         else:
-            raise ConnectionException('External connection exception occurred: ' + str(exc))
+            raise ConnectionException("External connection exception occurred: " + str(exc))
 
 
 # This is used to serialize the args in the run_results and in the logs.