diff --git a/plone/app/discussion/browser/comment.py b/plone/app/discussion/browser/comment.py
index ab5f32d..6497fec 100644
--- a/plone/app/discussion/browser/comment.py
+++ b/plone/app/discussion/browser/comment.py
@@ -2,7 +2,7 @@
 from AccessControl import getSecurityManager
 from Acquisition import aq_inner
 from Acquisition import aq_parent
-from comments import CommentForm
+from .comments import CommentForm
 from plone.app.discussion import _
 from plone.registry.interfaces import IRegistry
 from plone.z3cform.layout import wrap_form
diff --git a/plone/app/discussion/browser/comments.py b/plone/app/discussion/browser/comments.py
index c817517..2689c97 100644
--- a/plone/app/discussion/browser/comments.py
+++ b/plone/app/discussion/browser/comments.py
@@ -19,7 +19,7 @@ from plone.z3cform.interfaces import IWrappedForm
 from Products.CMFCore.utils import getToolByName
 from Products.Five.browser.pagetemplatefile import ViewPageTemplateFile
 from Products.statusmessages.interfaces import IStatusMessage
-from urllib import quote as url_quote
+from six.moves.urllib.parse import quote
 from z3c.form import button
 from z3c.form import field
 from z3c.form import form
@@ -537,7 +537,7 @@ class CommentsViewlet(ViewletBase):
     def login_action(self):
         return '{0}/login_form?came_from={1}'.format(
             self.navigation_root_url,
-            url_quote(self.request.get('URL', '')),
+            quote(self.request.get('URL', '')),
         )
 
     def format_time(self, time):
diff --git a/plone/app/discussion/catalog.py b/plone/app/discussion/catalog.py
index 1ada61b..97c5dc7 100644
--- a/plone/app/discussion/catalog.py
+++ b/plone/app/discussion/catalog.py
@@ -12,7 +12,6 @@ from plone.uuid.interfaces import IUUID
 from Products.CMFCore.interfaces import IContentish
 from Products.CMFPlone.utils import safe_unicode
 from Products.ZCatalog.interfaces import IZCatalog
-from string import join
 
 
 MAX_DESCRIPTION = 25
@@ -77,7 +76,7 @@ def creator(object):
 @indexer(IComment)
 def description(object):
     # Return the first 25 words of the comment text and append ' [...]'
-    text = join(object.getText(targetMimetype='text/plain').split()[:MAX_DESCRIPTION])
+    text = ' '.join(object.getText(targetMimetype='text/plain').split()[:MAX_DESCRIPTION])
     if len(object.getText().split()) > 25:
         text += ' [...]'
     return text
diff --git a/plone/app/discussion/tests/test_comments_viewlet.py b/plone/app/discussion/tests/test_comments_viewlet.py
index 630b237..6f2ff23 100644
--- a/plone/app/discussion/tests/test_comments_viewlet.py
+++ b/plone/app/discussion/tests/test_comments_viewlet.py
@@ -727,7 +727,7 @@ class TestCommentsViewlet(unittest.TestCase):
         )
 
     def test_format_time(self):
-        python_time = datetime(2009, 02, 01, 23, 32, 03, 57)
+        python_time = datetime(2009, 2, 1, 23, 32, 3, 57)
         # Python Time must be utc time. There seems to be no too simple way
         # to tell datetime to be of utc time.
         # therefor, we convert the time to seconds since epoch, which seems