Y wcfs: tests: Teach tSubProcess to run function from any module

We will soon need to use tSubProcess not only for tests and so will move
it out to another place. It will need to be able to run functions from
both wcfs/wcfs_faultyprot_test.py and from other modules. Prepare to
that.

wcfs/wcfs_faultyprot_test.py

@@ -25,7 +25,7 @@ from __future__ import print_function, absolute_import
 from wendelin.lib.zodb import zstor_2zurl
 from wendelin import wcfs
 
-import sys, os, subprocess, traceback
+import sys, os, subprocess, traceback, importlib
 import six
 from golang import select, func, defer
 from golang import context, sync, time
@@ -68,7 +68,7 @@ def with_prompt_pintimeout(monkeypatch):
 class tSubProcess(object):
     def __init__(proc, f, *argv, **kw):
         exev = [sys.executable, '-c', 'from wendelin.wcfs import wcfs_faultyprot_test as t; '
-                                      't.tSubProcess._start(%r)' % f.__name__]
+                                      't.tSubProcess._start(%r)' % '%s.%s' % (f.__module__, f.__name__)]
         proc.popen = subprocess.Popen(exev, stdin=subprocess.PIPE, stdout=subprocess.PIPE, close_fds=True)
         try:
             proc.cin  = MPConnection(os.dup(proc.popen.stdin.fileno()),  readable=False)
@@ -83,15 +83,17 @@ class tSubProcess(object):
 
     # _start is trampoline ran in the subprocess to launch to user function.
     @staticmethod
-    def _start(funcname):
+    def _start(funcpath):
         cin  = MPConnection(os.dup(sys.stdin.fileno()),  writable=False)
         cout = MPConnection(os.dup(sys.stdout.fileno()), readable=False)
         sys.stdin  = open(os.devnull, 'r')  # XXX better dup2 ?
         sys.stdout = open(os.devnull, 'w')
         argv = cin.recv()
         kw   = cin.recv()
-        f = globals()[funcname]
-        procname = kw.pop('_procname', f.__name__)
+        modname, funcname = funcpath.rsplit('.', 1)
+        mod = importlib.import_module(modname)
+        f = getattr(mod, funcname)
+        procname = kw.pop('_procname', funcpath)
         try:
             f(cin, cout, *argv, **kw)
             _ = 'END'