contrib: Detailed reporting for http errors in github-merge

Print detailed error, this makes it easier to diagnose github API issues.

contrib/devtools/github-merge.py

@@ -23,6 +23,7 @@
 import json
 import codecs
 from urllib.request import Request, urlopen
+from urllib.error import HTTPError
 
 # External tools (can be overridden using environment)
 GIT = os.getenv('GIT','git')
@@ -57,6 +58,11 @@ def retrieve_pr_info(repo,pull):
  reader = codecs.getreader('utf-8')
  obj = json.load(reader(result))
  return obj
+ except HTTPError as e:
+ error_message = e.read()
+ print('Warning: unable to retrieve pull information from github: %s' % e)
+ print('Detailed error: %s' % error_message)
+ return None
  except Exception as e:
  print('Warning: unable to retrieve pull information from github: %s' % e)
  return None