Merge ~larsks/cloud-init:feature/hide-oauthlib-import-failure into cloud-init:master

[Lars Kellogg-Stedman]

url_helper: fail gracefully if oauthlib is not available

We are unable to ship python-oauthlib in RHEL. This commit allows
imports of url_helper to succeed even when oauthlib is unavailable
and OauthUrlHelper.oauth_headers to raise a NotImplementedException
when called.

LP: #1713760

url_helper: fail gracefully if oauthlib is not available

We are unable to ship python-oauthlib in RHEL. This commit allows
imports of url_helper to succeed even when oauthlib is unavailable
and OauthUrlHelper.oauth_headers to raise a NotImplementedException
when called.

[Server Team CI bot (server-team-bot)]

PASSED: Continuous integration, rev:29025c3b9dd3ac1eb1d3858f9826adacdb700ac2
https://jenkins.ubuntu.com/server/job/cloud-init-ci/201/
Executed test runs:
    SUCCESS: Checkout
    SUCCESS: Unit & Style Tests
    SUCCESS: Ubuntu LTS: Build
    SUCCESS: Ubuntu LTS: Integration
    SUCCESS: MAAS Compatability Testing
    IN_PROGRESS: Declarative: Post Actions

Click here to trigger a rebuild:
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review: Approve (continuous-integration)

[Chad Smith (chad.smith)]

This branch is good as is, though I'd like to see a mocked ImportError test to confirm the raise NotImplementedError. Example is in tests/unittests/test_handler/test_schema.py

diff --git a/cloudinit/url_helper.py b/cloudinit/url_helper.py
index 7cf76aa..c83061a 100644
--- a/cloudinit/url_helper.py
+++ b/cloudinit/url_helper.py
@@ -17,7 +17,11 @@ import time
 from email.utils import parsedate
 from functools import partial
 
-import oauthlib.oauth1 as oauth1
+try:
+    import oauthlib.oauth1 as oauth1
+except ImportError:
+    oauth1 = None
+
 from requests import exceptions
 
 from six.moves.urllib.parse import (
@@ -488,6 +492,10 @@ class OauthUrlHelper(object):
 
 def oauth_headers(url, consumer_key, token_key, token_secret, consumer_secret,
                   timestamp=None):
+
+    if oauth1 is None:
+        raise NotImplementedError('oauth support is not available')
+
     if timestamp:
         timestamp = str(timestamp)
     else: