Fix the ClientSideError constructor so that it is propertly displayed in the backtrace

wsme/exc.py

@@ -1,11 +1,12 @@
 import six
-from six.moves import builtins
 
-if '_' not in builtins.__dict__:
-    builtins._ = lambda s: s
+from wsme.utils import _
 
 
 class ClientSideError(RuntimeError):
+    def __init__(self):
+        super(ClientSideError, self).__init__(self.faultstring)
+
     @property
     def faultstring(self):
         return str(self)
@@ -16,18 +17,20 @@ class InvalidInput(ClientSideError):
         self.fieldname = fieldname
         self.value = value
         self.msg = msg
+        super(InvalidInput, self).__init__()
 
     @property
     def faultstring(self):
         return _(six.u(
-            "Invalid input for field/attribute %s. Value: '%s'. %s")) % (
-                 self.fieldname, self.value, self.msg)
+            "Invalid input for field/attribute %s. Value: '%s'. %s")
+        ) % (self.fieldname, self.value, self.msg)
 
 
 class MissingArgument(ClientSideError):
     def __init__(self, argname, msg=''):
         self.argname = argname
         self.msg = msg
+        super(MissingArgument, self).__init__()
 
     @property
     def faultstring(self):
@@ -39,6 +42,7 @@ class UnknownArgument(ClientSideError):
     def __init__(self, argname, msg=''):
         self.argname = argname
         self.msg = msg
+        super(UnknownArgument, self).__init__()
 
     @property
     def faultstring(self):
@@ -49,6 +53,7 @@ class UnknownArgument(ClientSideError):
 class UnknownFunction(ClientSideError):
     def __init__(self, name):
         self.name = name
+        super(UnknownFunction, self).__init__()
 
     @property
     def faultstring(self):

wsme/utils.py

@@ -1,6 +1,7 @@
 import decimal
 import datetime
 import re
+from six.moves import builtins
 
 date_re = r'(?P<year>-?\d{4,})-(?P<month>\d{2})-(?P<day>\d{2})'
 time_re = r'(?P<hour>\d{2}):(?P<min>\d{2}):(?P<sec>\d{2})' + \
@@ -14,6 +15,13 @@ date_re = re.compile(date_re)
 time_re = re.compile(time_re)
 
 
+if hasattr(builtins, '_'):
+    _ = builtins._
+else:
+    def _(s):
+        return s
+
+
 def parse_isodate(value):
     m = date_re.match(value)
     if m is None: