Don't use singleton CredentialStore in requires_credentials decorator

Fix for jamesremuscat#10

src/pyze/api/credentials.py

@@ -20,8 +20,13 @@ class MissingCredentialException(Exception):
 def requires_credentials(*names):
     def _requires_credentials(func):
         def inner(*args, **kwargs):
+            credentials = None
+            if args[0] and hasattr(args[0], '_credentials'):
+                credentials = args[0]._credentials
+            elif args[0] and hasattr(args[0], '_kamereon'):
+                credentials = args[0]._kamereon._credentials
             for name in names:
-                if name not in CredentialStore():
+                if name not in credentials:
                     raise MissingCredentialException(name)
             return func(*args, **kwargs)
 
@@ -100,6 +105,11 @@ def _add_api_keys_from_env(self):
             if 'KAMEREON_API_KEY' in os.environ:
                 self.store('kamereon-api-key', os.environ['KAMEREON_API_KEY'], None)
 
+        def requires(self, *names):
+            for name in names:
+                if name not in self._store:
+                    raise MissingCredentialException(name)
+
 
 Credential = namedtuple(
     'Credential',