CA-121667 Fix DeprecationWarning when running on newer Python versions

popen2 has been deprecated on newer Python versions and generates a warning when xsconsole starts.
We always run on Python 2.4 or later, so we are safe to move to using the subprocess module in all cases.
Fix wrong syntax trowing exception.

Old syntax was used causing Exception to not being initialized as expected
(passing the string).

Signed-off-by: Frediano Ziglio <frediano.ziglio@citrix.com>
Import errno module to be able to use it

errno.EINTR is used in the code but errno module was not imported causing
error executing except path in the code.

Signed-off-by: Frediano Ziglio <frediano.ziglio@citrix.com>
Merge commit '4a7e1399932df89b63d5f56cdd5d248c103ff8ba'