gnu: python-google-api-client: Rewrite invalid setup.py.

The packages argument accepts package names only, not paths. Replacing
the slash with a dot allows passing the sanity-check phase, because the
submodule will not be listed in top_level.txt any more.

* gnu/packages/python-web.scm (python-google-api-client) [#:phases]:
Add new phase 'fix-setup-py.

gnu/packages/python-web.scm

@@ -4338,7 +4338,15 @@ (define-public python-google-api-client
          "1wpbbbxfpy9mwxdy3kn352cb590ladv574j1aa2l4grjdqw3ln05"))))
     (build-system python-build-system)
     (arguments
-     '(#:tests? #f)) ; tests require internet access
+     `(#:tests? #f ; tests require internet access
+       #:phases
+       (modify-phases %standard-phases
+         (add-after 'unpack 'fix-setup-py
+           (lambda _
+             (substitute* "setup.py"
+               (("googleapiclient/discovery_cache")
+                "googleapiclient.discovery_cache"))
+             #t)))))
     (native-inputs
      `(("python-httplib2" ,python-httplib2)
        ("python-six" ,python-six)