Allow logging of Content-Type text/plain

Noticed this while doing some local testing, if a WSGI app replies with
a text/plain content type to communicate a server error, we aren't able
to see the error response message when passing --debug to the
openstackclient, example:

  RESP: [500] Date: Thu, 01 Oct 2020 23:54:15 GMT Server: Apache/2.4.18
  (Ubuntu) Content-Type: text/plain; charset=UTF-8 Connection: close
  Transfer-Encoding: chunked
  RESP BODY: Omitted, Content-Type is set to text/plain; charset=UTF-8.
  Only application/json responses have their bodies logged.

Change-Id: Ibfd46c7725bd0aa26f1f80b0e8fc6eda2ac2e090

keystoneauth1/session.py

@@ -48,7 +48,7 @@ DEFAULT_USER_AGENT = 'keystoneauth1/%s %s %s/%s' % (
 # NOTE(jamielennox): Clients will likely want to print more than json. Please
 # propose a patch if you have a content type you think is reasonable to print
 # here and we'll add it to the list as required.
-_LOG_CONTENT_TYPES = set(['application/json'])
+_LOG_CONTENT_TYPES = set(['application/json', 'text/plain'])
 
 _MAX_RETRY_INTERVAL = 60.0
 _EXPONENTIAL_DELAY_START = 0.5

keystoneauth1/tests/unit/test_session.py

@@ -383,11 +383,13 @@ class SessionTests(utils.TestCase):
         """Verify response body is only logged in specific content types.
 
         Response bodies are logged only when the response's Content-Type header
-        is set to application/json. This prevents us to get an unexpected
-        MemoryError when reading arbitrary responses, such as streams.
+        is set to application/json or text/plain. This prevents us to get an
+        unexpected MemoryError when reading arbitrary responses, such as
+        streams.
         """
-        OMITTED_BODY = ('Omitted, Content-Type is set to %s. Only '
-                        'application/json responses have their bodies logged.')
+        OMITTED_BODY = ('Omitted, Content-Type is set to %s. Only ' +
+                        ', '.join(client_session._LOG_CONTENT_TYPES) +
+                        ' responses have their bodies logged.')
         session = client_session.Session(verify=False)
 
         # Content-Type is not set
@@ -422,6 +424,23 @@ class SessionTests(utils.TestCase):
         self.assertNotIn(OMITTED_BODY % 'application/json; charset=UTF-8',
                          self.logger.output)
 
+        # Content-Type is set to text/plain
+        text = 'Error detected, unable to continue.'
+        self.stub_url('POST', text=text,
+                      headers={'Content-Type': 'text/plain'})
+        session.post(self.TEST_URL)
+        self.assertIn(text, self.logger.output)
+        self.assertNotIn(OMITTED_BODY % 'text/plain', self.logger.output)
+
+        # Content-Type is set to text/plain; charset=UTF-8
+        text = 'Error detected, unable to continue.'
+        self.stub_url('POST', text=text,
+                      headers={'Content-Type': 'text/plain; charset=UTF-8'})
+        session.post(self.TEST_URL)
+        self.assertIn(text, self.logger.output)
+        self.assertNotIn(OMITTED_BODY % 'text/plain; charset=UTF-8',
+                         self.logger.output)
+
     def test_logging_cacerts(self):
         path_to_certs = '/path/to/certs'
         session = client_session.Session(verify=path_to_certs)