Try to work around hanging test on Travis CI*
Try to work around hanging test on Travis CI*

I think these changes should resolve the issue with hanging builds on
Travis CI first documented in 526cce7392d. I'm pretty sure I was able to
reproduce the problematic behavior using the following command line on
an Ubuntu 14.04 (Trusty) system:

  $ gpg-agent --daemon 2>&1 | cat
  GPG_AGENT_INFO=/tmp/gpg-cAjgER/S.gpg-agent:31308:1; export GPG_AGENT_INFO;
  gpg-agent[31308]: gpg-agent (GnuPG) 2.0.22 started

In the example above I didn't get control of the terminal back until I
pressed Control-C, but after I did so the gpg-agent background process
was still running (i.e. the Control-C didn't kill it).

xolox/python-proc,xolox/python-proc