Install 'grpc' deps for 'lint'; suppress 'pylint' import checks.

Rationale:

pylint tries to guess at imports in the 'google' namespace, and fails
miserably.  We test that those imports are valid all the time in unit tests
anyway, so just disable them in pylint.

Author: tseaver

gcloud/logging/_gax.py

@@ -16,7 +16,6 @@
 
 import json
 
-# pylint: disable=import-error
 from google.gax import CallOptions
 from google.gax import INITIAL_PAGE
 from google.gax.errors import GaxError
@@ -27,7 +26,6 @@
 from google.logging.v2.log_entry_pb2 import LogEntry
 from google.protobuf.json_format import Parse
 from grpc.beta.interfaces import StatusCode
-# pylint: enable=import-error
 
 from gcloud.exceptions import Conflict
 from gcloud.exceptions import NotFound

gcloud/pubsub/_gax.py

@@ -14,15 +14,13 @@
 
 """GAX wrapper for Pubsub API requests."""
 
-# pylint: disable=import-error
 from google.gax import CallOptions
 from google.gax import INITIAL_PAGE
 from google.gax.errors import GaxError
 from google.gax.grpc import exc_to_code
 from google.pubsub.v1.pubsub_pb2 import PubsubMessage
 from google.pubsub.v1.pubsub_pb2 import PushConfig
 from grpc.beta.interfaces import StatusCode
-# pylint: enable=import-error
 
 from gcloud.exceptions import Conflict
 from gcloud.exceptions import NotFound

scripts/pylintrc_default

@@ -77,6 +77,7 @@ load-plugins=pylint.extensions.check_docs
 #                          return int(value)
 #                      else:
 #                          return float(value)
+# - import-error: imports are checked via tests.
 # - wrong-import-position: This error is overzealous. It assumes imports are
 #                          completed whenever something non-trivial is
 #                          defined, e.g.
@@ -100,6 +101,7 @@ disable =
     similarities,
     star-args,
     redefined-variable-type,
+    import-error,
     wrong-import-position,
     no-name-in-module,
     missing-raises-doc,

tox.ini

@@ -143,11 +143,9 @@ commands =
     python {toxinidir}/scripts/pycodestyle_on_repo.py
     python {toxinidir}/scripts/run_pylint.py
 deps =
-    {[testing]deps}
+    {[testenv]deps}
     pycodestyle
     pylint >= 1.6.4
-setenv =
-    PYTHONPATH = {toxinidir}/_testing
 passenv = {[testenv:system-tests]passenv}
 
 [testenv:system-tests]