Capture the error output of a foreground command using plumbum
<p>I'm using the plumbum python library (http://plumbum.readthedocs.org/) as a replacement for shell scripts.</p>

<p>There's a command I want to run that, when it fails it outputs the paths to a file I'm interested in:</p>

<pre><code>$ slow_cmd
Working.... 0%
Working.... 5%
Working... 15%
FAIL. Check log/output.log for details
</code></pre>

<p>I want to run the program on the foreground to check the progress:</p>

<pre><code>from plumbum.cmd import slow_cmd

try:
    f = slow_cmd &amp; FG
except Exception, e:
    print "Something went wrong."

# Need the error output from f to get the log file :(    
</code></pre>

<p>When the <code>slow_cmd</code> fails, it throws the exception (which I can catch). But I cannot obtain the error output from the exception or from the <code>f</code> future object.</p>

<p>If I don't run the <code>slow_cmd</code> on the FG, the exception contains all of the output and I can read the file from there.</p>
