python3-urlgrabber does not exist in Ubuntu and missing urllib

[adivardi]

Hello,
I have 2 related issues:

1. It seems the package jsk_rqt_pkugins has a non-existing dependency. For python3, it specifies python3-urlgrabber. However, this package does not exist in Ubuntu. For Ubuntu 18.04, it is named python-urlgrabber for both python2 and python3. In Ubuntu 20.04 it does not exist at all.
   In any case, I could not find where this dependency is even used, so maybe should consider removing it.

2. Following the first issue, I noticed the only packages which uses anything related to url handling are jsk_interactive_test and the travis submodule. For jsk_interactive_test, you actually use urllib2 and urllib, not urlgrabber. Following the commit history, I think the urlgrabber dep was probably add by mistake and to the wrong package.

I suggest removing completely the python-urlgrabber dep and adding urllib. Though I suspect you are using a different distribution than me, so I would like to confirm this makes sense before making any fixes.