fix back compat issues with python modules

When using python-daemon 1.6, the interface has changed in an
uncompatible way. Clark pointed me to Gerritbot which solves that issue
with a simple try / catch block implemented with:

b2be72e69d

So this patch is merely a copy/paste from David "davido" Ostrovsky with
a small workaround for pyflakes issue #13 (we have to prented we are
using the variable holding the module).

Change-Id: Iffdf7fca067734fa9c09b5bddfb13f122e6251a7
Reviewed-on: https://review.openstack.org/13524
Reviewed-by: Monty Taylor <mordred@inaugust.com>
Reviewed-by: James E. Blair <corvus@inaugust.com>
Approved: James E. Blair <corvus@inaugust.com>
Tested-by: Jenkins

zuul-server

@@ -16,7 +16,15 @@
 import argparse
 import ConfigParser
 import daemon
-import daemon.pidlockfile
+
+try:
+    import daemon.pidlockfile as pid_file_module
+    pid_file_module # workaround for pyflakes issue #13
+except:
+    # as of python-daemon 1.6 it doesn't bundle pidlockfile anymore
+    # instead it depends on lockfile-0.9.1 which uses pidfile.
+    import daemon.pidfile as pid_file_module
+
 import logging.config
 import os
 import signal
@@ -120,7 +128,7 @@ if __name__ == '__main__':
         pid_fn = os.path.expanduser(server.config.get('zuul', 'pidfile'))
     else:
         pid_fn = '/var/run/zuul/zuul.pid'
-    pid = daemon.pidlockfile.TimeoutPIDLockFile(pid_fn, 10)
+    pid = pid_file_module.TimeoutPIDLockFile(pid_fn, 10)
 
     if server.args.nodaemon:
         server.setup_logging()