diff --git a/kallithea/bin/base.py b/kallithea/bin/base.py
--- a/kallithea/bin/base.py
+++ b/kallithea/bin/base.py
@@ -108,7 +108,7 @@ class RcConf(object):
     def __getitem__(self, key):
         return self._conf[key]
 
-    def __nonzero__(self):
+    def __bool__(self):
         if self._conf:
             return True
         return False
diff --git a/kallithea/lib/auth.py b/kallithea/lib/auth.py
--- a/kallithea/lib/auth.py
+++ b/kallithea/lib/auth.py
@@ -760,7 +760,7 @@ class _PermsFunction(object):
     def __init__(self, *required_perms):
         self.required_perms = required_perms # usually very short - a list is thus fine
 
-    def __nonzero__(self):
+    def __bool__(self):
         """ Defend against accidentally forgetting to call the object
             and instead evaluating it directly in a boolean context,
             which could have security implications.
diff --git a/kallithea/lib/rcmail/response.py b/kallithea/lib/rcmail/response.py
--- a/kallithea/lib/rcmail/response.py
+++ b/kallithea/lib/rcmail/response.py
@@ -87,7 +87,7 @@ class MailBase(object):
     def __delitem__(self, key):
         del self.headers[normalize_header(key)]
 
-    def __nonzero__(self):
+    def __bool__(self):
         return self.body is not None or len(self.headers) > 0 or len(self.parts) > 0
 
     def keys(self):