resiliencytest.slaprunner: Add error log when contacting slaprunner.

/reviewed-on !38

slapos/resiliencytest/suites/slaprunner.py

@@ -85,6 +85,7 @@ class SlaprunnerTestSuite(ResiliencyTestSuite):
     Connect through HTTP to the slaprunner instance.
     Require self.slaprunner_backend_url to be set.
     """
+    try:
       url = "%s/%s" % (self.slaprunner_backend_url, resource)
       if data:
         result = self._opener_director.open(url, data=data)
@@ -94,6 +95,9 @@ class SlaprunnerTestSuite(ResiliencyTestSuite):
       if result.getcode() is not 200:
         raise NotHttpOkException(result.getcode())
       return result.read()
+    except urllib2.HTTPError:
+      self.logger.error('Error when contacting slaprunner at URL: {}'.format(url))
+      raise
 
   def _login(self):
     self.logger.debug('Logging in...')