lfs: dump the full response on httperror in debug mode

This was immensely helpful in diagnosing the 500: Internal Server Error when
using workers to upload.  It's a nasty wall of html, so we really can't do
anything else with it.

hgext/lfs/blobstore.py

@@ -312,6 +312,8 b' class _gitlfsremote(object):'
                 if response:
                     self.ui.debug('lfs %s response: %s' % (action, response))
         except util.urlerr.httperror as ex:
+            if self.ui.debugflag:
+                self.ui.debug('%s: %s' % (oid, ex.read()))
             raise LfsRemoteError(_('HTTP error: %s (oid=%s, action=%s)')
                                  % (ex, oid, action))