[Backport branch-7-6] Improved initial check on generating reference maps, avoid crash with label styles (symbol errors), removed dead code.

[MapServer-backport-bot]

Backport 00e5b98 from #6297

[jmckenna]

@sdlime sorry to sound annoying, but do you mind editing the title of this pull request (because when I generate the changelog for the release later, the summary for this change will only say "fix a couple of things"...and usually when this happens in the changelog i have to manually go find the ticket and update the changelog html with better description, for the readers). thanks!

[sdlime]

@sdlime sorry to sound annoying, but do you mind editing the title of this pull request (because when I generate the changelog for the release later, the summary for this change will only say "fix a couple of things"...and usually when this happens in the changelog i have to manually go find the ticket and update the changelog html with better description, for the readers). thanks!

Sorry, no problem. Main has the old description though - can that be changed?

[sdlime]

TravisCI died for a reason other than my changes - which were pretty benign.

[rouault]

TravisCI died for a reason other than my changes

TravisCI for the 7.6 branch is defunct. Proably due to Trusty being too old or python 2.7 choking with pip.

[jmckenna]

All has been well in branch-7-6 until a change a few days ago....will investigate now....

[jmckenna]

regarding Python 2.7 and PIP, we should not rely on such an old release (I think this was a change recently, for pip to run with a dev's older Python 2.7). But obviously that is not sustainable (good word), so let's put that back to run on Python3......looking now...

[dmorissette]

@jmckenna if you are alluding to PR #6285, then for the record the "dev's old python 2.7" you are alluding to is actually our official Vagrant config (and not my or anyone's old python 2.7). This Vagrant config is required to update/upgrade msautotest results. Full story in the PR.

[jmckenna]

ah thanks @dmorissette, I was assuming our vagrant config was changed for Python 2.7, sorry my mistake.

[jmckenna]

By the way, great to see so many watching so closely! This is a good problem to have :)

[jmckenna]

Gotta love open source, only way to get people to speak-up is to make a mistake :)