fix httpretty based test cases if http_proxy is set.

previously this would fail:
  http_proxy=http://foo.bar make test

now it will pass.  This works around a bug where httpretty is not able to
patch http operations if http_proxy is set.

https://github.com/gabrielfalcao/HTTPretty/issues/122

tests/unittests/helpers.py

@@ -233,6 +233,21 @@ class FilesystemMockingTestCase(ResourceUsingTestCase):
                 self.patched_funcs.append((mod, f, func))
 
 
+class HttprettyTestCase(TestCase):
+    # necessary as http_proxy gets in the way of httpretty
+    # https://github.com/gabrielfalcao/HTTPretty/issues/122
+    def setUp(self):
+        self.restore_proxy = os.environ.get('http_proxy')
+        if self.restore_proxy is not None:
+            del os.environ['http_proxy']
+        super(HttprettyTestCase, self).setUp()
+
+    def tearDown(self):
+        if self.restore_proxy:
+            os.environ['http_proxy'] = self.restore_proxy
+        super(HttprettyTestCase, self).tearDown()
+
+
 def populate_dir(path, files):
     if not os.path.exists(path):
         os.makedirs(path)

tests/unittests/test_datasource/test_gce.py

@@ -55,12 +55,13 @@ def _request_callback(method, uri, headers):
         return (404, headers, '')
 
 
-class TestDataSourceGCE(test_helpers.TestCase):
+class TestDataSourceGCE(test_helpers.HttprettyTestCase):
 
     def setUp(self):
         self.ds = DataSourceGCE.DataSourceGCE(
             settings.CFG_BUILTIN, None,
             helpers.Paths({}))
+        super(TestDataSourceGCE, self).setUp()
 
     @httpretty.activate
     def test_connection(self):

tests/unittests/test_datasource/test_openstack.py

@@ -121,7 +121,7 @@ def _register_uris(version, ec2_files, ec2_meta, os_files):
                     body=get_request_callback)
 
 
-class TestOpenStackDataSource(test_helpers.TestCase):
+class TestOpenStackDataSource(test_helpers.HttprettyTestCase):
     VERSION = 'latest'
 
     @hp.activate

tests/unittests/test_ec2_util.py

@@ -6,7 +6,7 @@ from cloudinit import url_helper as uh
 import httpretty as hp
 
 
-class TestEc2Util(helpers.TestCase):
+class TestEc2Util(helpers.HttprettyTestCase):
     VERSION = 'latest'
 
     @hp.activate