DRY (Do not repeat yourself) - Branch name should be global constant

[mithro]

Currently the code is littered with 'pullrequest/temp/{0}/{1}/{2} like sequences. This makes it hard to quickly change the sequence. It should be something like;

GH_PULLREQUEST_NAMESPACE = 'pullrequest/temp/{pr_id}/{seq_id}/{branch}'

def myfunc(xxx):
    a = GH_PULLREQUEST_NAMESPACE.format(pr_id=pull_request_id, seq_id=0, branch='master')