adds gcsfs to nox smoke, adds not implimented error to core

Author: andrewfulton9

noxfile.py

@@ -27,7 +27,7 @@ def install(session):
 
 @nox.session(python=False)
 def smoke(session):
-    session.install(*"pytest aiohttp requests".split())
+    session.install(*"pytest aiohttp requests gcsfs".split())
     session.run(*"pytest --skiphdfs upath".split())
 
 

upath/core.py

@@ -273,6 +273,9 @@ def is_file(self):
             return True
         return False
 
+    def chmod(self, mod):
+        raise NotImplementedError
+
     def rename(self, target):
         # can be implemented, but may be tricky
         raise NotImplementedError