diff --git a/ckan/controllers/error.py b/ckan/controllers/error.py
index d03b112ef14..5bca6ab20fe 100644
--- a/ckan/controllers/error.py
+++ b/ckan/controllers/error.py
@@ -11,6 +11,7 @@
 from ckan.lib.base import render
 from ckan.lib.helpers import literal
 
+
 class ErrorController(BaseController):
     """Generates error documents as and when they are required.
 
diff --git a/ckan/lib/helpers.py b/ckan/lib/helpers.py
index e8a94e74b0a..557a4f472d2 100644
--- a/ckan/lib/helpers.py
+++ b/ckan/lib/helpers.py
@@ -776,11 +776,11 @@ def _create_link_text(text, **kwargs):
         return text
 
     icon = kwargs.pop('icon', None)
-    class_ = _link_class(kwargs)
+    cls = _link_class(kwargs)
     return link_to(
         _create_link_text(text, **kwargs),
         url_for(*args, **kwargs),
-        class_=class_
+        cls=cls
     )
 
 
@@ -791,7 +791,11 @@ def _preprocess_dom_attrs(attrs):
     like `class` that cannot be used because it special meaning in
     Python.
     """
-    return {key.rstrip('_'): value for key, value in attrs.items()}
+    return {
+        key.rstrip('_'): value
+        for key, value in attrs.items()
+        if value is not None
+    }
 
 
 def _make_safe_id_component(idstring):
@@ -806,7 +810,7 @@ def _make_safe_id_component(idstring):
 
     Whitespace is transformed into underscores, and then
     anything which is not a hyphen or a character that
-    matches \w (alphanumerics and underscore) is removed.
+    matches \\w (alphanumerics and underscore) is removed.
 
     """
     # Transform all whitespace to underscore
@@ -1351,7 +1355,7 @@ def truncate(text, length=30, indicator='...', whole_word=False):
     if i <= 0:
         # Entire text before break is one word, or we miscalculated.
         return text[:short_length] + indicator
-    return text[:i+1] + indicator
+    return text[:i + 1] + indicator
 
 
 @core_helper
diff --git a/ckan/lib/pagination.py b/ckan/lib/pagination.py
index 9c90b86e37b..b20a335b462 100644
--- a/ckan/lib/pagination.py
+++ b/ckan/lib/pagination.py
@@ -145,7 +145,8 @@ def __init__(
             self.page_count = ((self.item_count - 1) / self.items_per_page) + 1
             self.last_page = self.first_page + self.page_count - 1
 
-            # Make sure that the requested page number is the range of valid pages
+            # Make sure that the requested page number is the range of
+            # valid pages
             if self.page > self.last_page:
                 self.page = self.last_page
             elif self.page < self.first_page:
@@ -241,8 +242,7 @@ def pager(
         dotdot_attr={u"class": u"pager_dotdot"},
         **kwargs
     ):
-        """
-        Return string with links to other pages (e.g. "1 2 [3] 4 5 6 7").
+        """Return string with links to other pages (e.g. "1 2 [3] 4 5 6 7").
 
         format:
             Format string that defines how the pager is rendered. The string
@@ -374,10 +374,10 @@ def pager(
             Default: { 'class':'pager_dotdot' }
 
         onclick (optional)
-            This paramter is a string containing optional Javascript code
-            that will be used as the 'onclick' action of each pager link.
-            It can be used to enhance your pager with AJAX actions loading another
-            page into a DOM object.
+            This paramter is a string containing optional Javascript
+            code that will be used as the 'onclick' action of each
+            pager link.  It can be used to enhance your pager with
+            AJAX actions loading another page into a DOM object.
 
             In this string the variable '$partial_url' will be replaced by
             the URL linking to the desired page with an added 'partial=1'
@@ -385,27 +385,34 @@ def pager(
             In addition the '$page' variable gets replaced by the
             respective page number.
 
-            Note that the URL to the destination page contains a 'partial_param'
-            parameter so that you can distinguish between AJAX requests (just
-            refreshing the paginated area of your page) and full requests (loading
-            the whole new page).
+            Note that the URL to the destination page contains a
+            'partial_param' parameter so that you can distinguish
+            between AJAX requests (just refreshing the paginated area
+            of your page) and full requests (loading the whole new
+            page).
 
-            [Backward compatibility: you can use '%s' instead of '$partial_url']
+            [Backward compatibility: you can use '%s' instead of
+            '$partial_url']
 
             jQuery example:
                 "$('#my-page-area').load('$partial_url'); return false;"
 
             Yahoo UI example:
                 "YAHOO.util.Connect.asyncRequest('GET','$partial_url',{
-                    success:function(o){YAHOO.util.Dom.get('#my-page-area').innerHTML=o.responseText;}
-                    },null); return false;"
+                    success:function(o){
+                        YAHOO.util.Dom.get(
+                            '#my-page-area'
+                        ).innerHTML=o.responseText;
+                    }
+                },null); return false;"
 
             scriptaculous example:
                 "new Ajax.Updater('#my-page-area', '$partial_url',
                     {asynchronous:true, evalScripts:true}); return false;"
 
             ExtJS example:
-                "Ext.get('#my-page-area').load({url:'$partial_url'}); return false;"
+                "Ext.get('#my-page-area').load({url:'$partial_url'});
+                return false;"
 
             Custom example:
                 "my_load_page($page)"
@@ -413,6 +420,7 @@ def pager(
         Additional keyword arguments are used as arguments in the links.
         Otherwise the link will be created with url_for() which points
         to the page you are currently displaying.
+
         """
         self.curpage_attr = curpage_attr
         self.separator = separator
@@ -430,7 +438,7 @@ def pager(
             return u""
 
         # Replace ~...~ in token format by range of pages
-        result = re.sub(r"~(\d+)~", self._range, format)
+        result = re.sub(u"~(\\d+)~", self._range, format)
 
         # Interpolate '%' variables
         result = Template(result).safe_substitute(
@@ -460,7 +468,7 @@ def pager(
 
         return Markup(result)
 
-    #### Private methods ####
+    # Private methods
     def _range(self, regexp_match):
         """
         Return range of linked pages (e.g. '1 2 [3] 4 5 6 7 8').
@@ -563,7 +571,9 @@ def _pagerlink(self, page, text):
             # updates)
             link_params[self.partial_param] = 1
             partial_url = url_generator(**link_params)
-            try:  # if '%s' is used in the 'onclick' parameter (backwards compatibility)
+            try:
+                # if '%s' is used in the 'onclick' parameter
+                # (backwards compatibility)
                 onclick_action = self.onclick % (partial_url,)
             except TypeError:
                 onclick_action = Template(self.onclick).safe_substitute(
diff --git a/ckan/tests/legacy/functional/api/test_package_search.py b/ckan/tests/legacy/functional/api/test_package_search.py
index 31792d3cc71..55b73765925 100644
--- a/ckan/tests/legacy/functional/api/test_package_search.py
+++ b/ckan/tests/legacy/functional/api/test_package_search.py
@@ -2,7 +2,7 @@
 
 from six.moves.urllib.parse import quote
 
-import webhelpers
+from dominate.util import escape
 
 import ckan.lib.search as search
 from ckan.tests.legacy import setup_test_search_index
@@ -64,7 +64,7 @@ def test_04_post_json(self):
         assert res_dict['result']['count'] == 1, res_dict['result']['count']
 
     def test_06_uri_q_tags(self):
-        query = webhelpers.util.html_escape('annakarenina tags:russian tags:tolstoy')
+        query = escape('annakarenina tags:russian tags:tolstoy')
         offset = self.base_url + '?q=%s' % query
         res = self.app.get(offset, status=200)
         res_dict = self.data_from_res(res)
diff --git a/ckan/tests/legacy/lib/test_helpers.py b/ckan/tests/legacy/lib/test_helpers.py
index 5516c2808b6..e1b2eda14ac 100644
--- a/ckan/tests/legacy/lib/test_helpers.py
+++ b/ckan/tests/legacy/lib/test_helpers.py
@@ -64,7 +64,7 @@ def test_time_ago_in_words_from_str(self):
         two_months_ago = datetime.datetime.now() - datetime.timedelta(days=65)
         two_months_ago_str = two_months_ago.isoformat()
         res = h.time_ago_in_words_from_str(two_months_ago_str)
-        assert_equal(res, '2 months')
+        assert_equal(res, '2 months ago')
 
     def test_gravatar(self):
         email = 'zephod@gmail.com'
diff --git a/ckan/tests/lib/test_helpers.py b/ckan/tests/lib/test_helpers.py
index fcb7cfb80b1..7c918f845d1 100644
--- a/ckan/tests/lib/test_helpers.py
+++ b/ckan/tests/lib/test_helpers.py
@@ -420,13 +420,13 @@ def test_internal_tag_link(self):
     def test_internal_tag_linked_with_quotes(self):
         """Asserts links like 'tag:"test-tag"' work"""
         data = 'tag:"test-tag" foobar'
-        output = '<p><a href="/dataset/?tags=test-tag">tag:&#34;test-tag&#34;</a> foobar</p>'
+        output = '<p><a href="/dataset/?tags=test-tag">tag:&quot;test-tag&quot;</a> foobar</p>'
         eq_(h.render_markdown(data), output)
 
     def test_internal_tag_linked_with_quotes_and_space(self):
         """Asserts links like 'tag:"test tag"' work"""
         data = 'tag:"test tag" foobar'
-        output = '<p><a href="/dataset/?tags=test+tag">tag:&#34;test tag&#34;</a> foobar</p>'
+        output = '<p><a href="/dataset/?tags=test+tag">tag:&quot;test tag&quot;</a> foobar</p>'
         eq_(h.render_markdown(data), output)
 
     def test_internal_tag_with_no_opening_quote_only_matches_single_word(self):
@@ -450,7 +450,7 @@ def test_internal_tag_with_no_closing_quote_does_not_match(self):
     def test_tag_names_match_simple_punctuation(self):
         """Asserts punctuation and capital letters are matched in the tag name"""
         data = 'tag:"Test- _." foobar'
-        output = '<p><a href="/dataset/?tags=Test-+_.">tag:&#34;Test- _.&#34;</a> foobar</p>'
+        output = '<p><a href="/dataset/?tags=Test-+_.">tag:&quot;Test- _.&quot;</a> foobar</p>'
         eq_(h.render_markdown(data), output)
 
     def test_tag_names_do_not_match_commas(self):
@@ -471,7 +471,7 @@ def test_tag_names_dont_match_non_space_whitespace(self):
     def test_tag_names_with_unicode_alphanumeric(self):
         """Asserts that unicode alphanumeric characters are captured"""
         data = u'tag:"Japanese katakana \u30a1" blah'
-        output = u'<p><a href="/dataset/?tags=Japanese+katakana+%E3%82%A1">tag:&#34;Japanese katakana \u30a1&#34;</a> blah</p>'
+        output = u'<p><a href="/dataset/?tags=Japanese+katakana+%E3%82%A1">tag:&quot;Japanese katakana \u30a1&quot;</a> blah</p>'
         eq_(h.render_markdown(data), output)
 
     def test_normal_link(self):