All resources to be found through exception deferral

There are situations where a given api service unrelated to the
requested resource is unavailable and an ServiceUnavailableError
exception is thrown.

The change in this PR will allow resources to be found if the
resource being requested is unrelated to an api service that is
unavailable.

Resolves openshift#349

Author: wmlynch

openshift/dynamic/discovery.py

@@ -9,7 +9,7 @@
 from urllib3.exceptions import ProtocolError, MaxRetryError
 
 from openshift import __version__
-from .exceptions import ResourceNotFoundError, ResourceNotUniqueError, ApiException
+from .exceptions import ResourceNotFoundError, ResourceNotUniqueError, ApiException, ServiceUnavailableError
 from .resource import Resource, ResourceList
 
 
@@ -29,6 +29,7 @@ def __init__(self, client, cache_file):
         default_cachefile_name = 'osrcp-{0}.json'.format(hashlib.sha1(self.__get_default_cache_id()).hexdigest())
         self.__cache_file = cache_file or os.path.join(tempfile.gettempdir(), default_cachefile_name)
         self.__init_cache()
+        self.__deferred_exception = None
 
     def __get_default_cache_id(self):
         user = self.__get_user()
@@ -182,7 +183,11 @@ def get_resources_for_api_version(self, prefix, group, version, preferred):
         subresources = {}
 
         path = '/'.join(filter(None, [prefix, group, version]))
-        resources_response = self.client.request('GET', path).resources or []
+        try:
+            resources_response = self.client.request('GET', path).resources or []
+        except ServiceUnavailableError as e:
+            self.__deferred_exception = e
+            resources_response = []
 
         resources_raw = list(filter(lambda resource: '/' not in resource['name'], resources_response))
         subresources_raw = list(filter(lambda resource: '/' in resource['name'], resources_response))
@@ -240,7 +245,7 @@ def get(self, **kwargs):
         if len(results) == 1:
             return results[0]
         elif not results:
-            raise ResourceNotFoundError('No matches found for {}'.format(kwargs))
+            raise self.__deferred_exception or ResourceNotFoundError('No matches found for {}'.format(kwargs))
         else:
             raise ResourceNotUniqueError('Multiple matches found for {}: {}'.format(kwargs, results))