diff --git a/src/calibre/gui2/dialogs/tag_categories.py b/src/calibre/gui2/dialogs/tag_categories.py
index 2446ddd9fb..d48ae9117f 100644
--- a/src/calibre/gui2/dialogs/tag_categories.py
+++ b/src/calibre/gui2/dialogs/tag_categories.py
@@ -12,7 +12,7 @@ from calibre.constants import islinux
 from calibre.utils.icu import sort_key, strcmp
 
 
-class Item:
+class Item(object):
 
     def __init__(self, name, label, index, icon, exists):
         self.name = name
@@ -22,7 +22,7 @@ class Item:
         self.exists = exists
 
     def __str__(self):
-        return 'name=%s, label=%s, index=%s, exists='%(self.name, self.label, self.index, self.exists)
+        return 'name=%s, label=%s, index=%s, exists=%s'%(self.name, self.label, self.index, self.exists)
 
 
 class TagCategories(QDialog, Ui_TagCategories):
diff --git a/src/calibre/srv/ajax.py b/src/calibre/srv/ajax.py
index 06eeacebdd..0b1741401a 100644
--- a/src/calibre/srv/ajax.py
+++ b/src/calibre/srv/ajax.py
@@ -475,7 +475,7 @@ def books_in(ctx, rd, encoded_category, encoded_item, library_id):
         try:
             dname, ditem = map(decode_name, (encoded_category, encoded_item))
         except:
-            raise HTTPNotFound('Invalid encoded param: %r' % (encoded_category, encoded_item))
+            raise HTTPNotFound('Invalid encoded param: %r (%r)' % (encoded_category, encoded_item))
         num, offset = get_pagination(rd.query)
         sort, sort_order = rd.query.get('sort', 'title'), rd.query.get('sort_order')
         sort_order = ensure_val(sort_order, 'asc', 'desc')
diff --git a/src/calibre/srv/tests/auth.py b/src/calibre/srv/tests/auth.py
index 876c00c427..6fc7f8739f 100644
--- a/src/calibre/srv/tests/auth.py
+++ b/src/calibre/srv/tests/auth.py
@@ -71,7 +71,7 @@ def digest(un, pw, nonce=None, uri=None, method='GET', nc=1, qop='auth', realm=R
         def __init__(self):
             self.method = method
 
-        def peek():
+        def peek(self):
             return body
     response = da.request_digest(pw, Data())
     return ('Digest ' + templ.format(
diff --git a/src/calibre/web/feeds/news.py b/src/calibre/web/feeds/news.py
index 10bcff67c2..a7c814e533 100644
--- a/src/calibre/web/feeds/news.py
+++ b/src/calibre/web/feeds/news.py
@@ -452,7 +452,7 @@ class BasicNewsRecipe(Recipe):
         return self.feeds
 
     @classmethod
-    def print_version(self, url):
+    def print_version(cls, url):
         '''
         Take a `url` pointing to the webpage with article content and return the
         :term:`URL` pointing to the print version of the article. By default does