old vs new string formatting method

[Marcin Gierdalski]

@joshswimlane :

I believe there is a bug in serviceendpoint.py that throws an error on me:
TypeError: not all arguments converted during string formatting

It is triggered by the line 105: raise SoapResponseHasError('Unable to parse respon@swmse from {current}' % self.__class__.__name__)
It looks like an inadvertent mix of old and new string formatting methods.

See line 103 for comparison: raise SoapAccessDeniedError('%s' % parsed_response.find('MessageText').string), which has it right using the old method.