Assign attributes for pygit2 callbacks

def setup_callbacks(self):
        '''
        Assign attributes for pygit2 callbacks
        '''
        if PYGIT2_VERSION >= _LooseVersion('0.23.2'):
            self.remotecallbacks = pygit2.RemoteCallbacks(
                credentials=self.credentials)
            if not self.ssl_verify:
                # Override the certificate_check function with a lambda that
                # just returns True, thus skipping the cert check.
                self.remotecallbacks.certificate_check = \
                    lambda *args, **kwargs: True
        else:
            self.remotecallbacks = None
            if not self.ssl_verify:
                warnings.warn(
                    'pygit2 does not support disabling the SSL certificate '
                    'check in versions prior to 0.23.2 (installed: {0}). '
                    'Fetches for self-signed certificates will fail.'.format(
                        PYGIT2_VERSION
                    )
                )