crontab -l error msgs are printed on screen, if no previous crontab file exists for user

On Linux and Solaris (and perhaps other platforms as well), when creating a cron for a user which previously had no crontab file, a text is written to stderr, and therefore to screen/console.

For example, in linux the message is:

no crontab for root

The solution is probably to replace the line in the Crontab.read method:
p = sp.Popen(self._read_execute(), stdout=sp.PIPE)

With the line:
p = sp.Popen(self._read_execute(), stdout=sp.PIPE, stderr=sp.PIPE)

And then the msg isn't displayed on screen (unless you choose to display it).

I tried this on a local copy, and it works perfectly.