accessing pending_gpg_keys using the api fails to some users

[Ursula Junque]

As seen on OOPS-1563B1563 and several others:
  TypeError: cannot create weak reference to 'unicode' object

Steps to reproduce:
1) Log in to devel api instance (service_root='https://api.edge.launchpad.net/devel/')
2) Try to access one of these users' pending_gpg_keys: almu, dalep1, jza873, kayalemao, nitalynx, which can be found on oops reports. I checked on launchpad and the users seem active.

I was successful accessing pending_gpg_keys to the following users: ursinha, matsubara (other than me), rsalveti (one outside lp teams), yada (a user without keys). All returned no results, but haven't failed.

[Curtis Hovey (sinzui)]

<gary_poster>
from canonical.launchpad.webapp.dbpolicy import MasterDatabasePolicy
 with MasterDatabasePolicy():
     (block of things that need to happen on master)
 That's what I was looking for. You can tell me whenever if that actually addresses the problem, or if we need to talk more