kubernetes: handle situation where the configuration is empty

This change is a follow-up to I5bdd369f6c9a78e5f79a926d8690f285fda94af9
where it missed the case where the configuration could be None.

Change-Id: I613cbf82932e14a8048e4dcfbf539fe1d83bf9e3

nodepool/driver/utils_k8s.py

@@ -41,10 +41,11 @@ def get_client(log, context, extra_client_constructor=None):
     token, ca, client, extra_client = None, None, None, None
     try:
         conf = _get_conf(log, context)
-        auth = conf.configuration.api_key.get('authorization')
-        if auth:
-            token = auth.split()[-1]
-        if conf.configuration.ssl_ca_cert:
+        if conf:
+            auth = conf.configuration.api_key.get('authorization')
+            if auth:
+                token = auth.split()[-1]
+        if conf and conf.configuration.ssl_ca_cert:
             with open(conf.configuration.ssl_ca_cert) as ca_file:
                 ca = ca_file.read()
                 ca = base64.b64encode(ca.encode('utf-8')).decode('utf-8')

releasenotes/notes/fix-k8s-conf-loading-a54a371a3392f665.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Fix Kubernetes in-cluster configuration loading if no local config
+    is present.  The previous release missed a fallback case which has
+    been corrected.