fix bug when HTTPS verification is disabled

pyotrs/lib.py

@@ -767,6 +767,8 @@ class Client(object):
                 if not os.path.isfile(ca_certs):
                     raise ValueError("Certificate file does not exist: {0}".format(ca_certs))
                 self.https_verify = ca_certs
+        else:
+            self.https_verify = False
 
         if operation_map:
             self.operation_map = operation_map