Make dependancy adal optional

Author: iamneha

config/kube_config.py

@@ -21,7 +21,6 @@
 import tempfile
 import time
 
-import adal
 import google.auth
 import google.auth.transport.requests
 import oauthlib.oauth2
@@ -36,6 +35,11 @@
 from .config_exception import ConfigException
 from .dateutil import UTC, format_rfc3339, parse_rfc3339
 
+try:
+    import adal
+except ImportError:
+    pass
+
 EXPIRY_SKEW_PREVENTION_DELAY = datetime.timedelta(minutes=5)
 KUBE_CONFIG_DEFAULT_LOCATION = os.environ.get('KUBECONFIG', '~/.kube/config')
 _temp_files = {}
@@ -218,21 +222,24 @@ def _load_azure_token(self, provider):
         return self.token
 
     def _refresh_azure_token(self, config):
-        tenant = config['tenant-id']
-        authority = 'https://login.microsoftonline.com/{}'.format(tenant)
-        context = adal.AuthenticationContext(
-            authority, validate_authority=True,
-        )
-        refresh_token = config['refresh-token']
-        client_id = config['client-id']
-        token_response = context.acquire_token_with_refresh_token(
-            refresh_token, client_id, '00000002-0000-0000-c000-000000000000')
-
-        provider = self._user['auth-provider']['config']
-        provider.value['access-token'] = token_response['accessToken']
-        provider.value['expires-on'] = token_response['expiresOn']
-        if self._config_persister:
-            self._config_persister(self._config.value)
+        if 'adal' not in globals():
+            raise ImportError('refresh token error, adal library not imported')
+        else:
+            tenant = config['tenant-id']
+            authority = 'https://login.microsoftonline.com/{}'.format(tenant)
+            context = adal.AuthenticationContext(
+                authority, validate_authority=True,
+            )
+            refresh_token = config['refresh-token']
+            client_id = config['client-id']
+            token_response = context.acquire_token_with_refresh_token(
+                refresh_token, client_id, '00000002-0000-0000-c000-000000000000')
+
+            provider = self._user['auth-provider']['config']
+            provider.value['access-token'] = token_response['accessToken']
+            provider.value['expires-on'] = token_response['expiresOn']
+            if self._config_persister:
+                self._config_persister(self._config.value)
 
     def _load_gcp_token(self, provider):
         if (('config' not in provider) or