Fix MillePede workflow using weights for the input data (Backport of #13321).

[ghellwig]

• strip off a possible weight directive before checking if file exists
• added more logging to detect possible misconfiguration

Backport of #13321

[cmsbuild]

A new Pull Request was created by @ghellwig (Gregor Mittag) for CMSSW_7_5_X.

It involves the following packages:

Alignment/MillePedeAlignmentAlgorithm

@diguida, @cerminar, @cmsbuild, @franzoni, @mmusich, @davidlange6 can you please review it and eventually sign? Thanks.
@mschrode, @mmusich, @tocheng, @tlampen this is something you requested to watch as well.
@slava77, @Degano, @smuzaffar you are the release manager for this.

cms-bot commands are list here #13028

[mmusich]

please test

[cmsbuild]

The tests are being triggered in jenkins.
https://cmssdt.cern.ch/jenkins/job/ib-any-integration/11275/console

[cmsbuild]

+1
Tested at: 21e8142
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-13323/11275/summary.html

[cmsbuild]

Comparison is ready
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-13323/11275/summary.html

[mmusich]

+1

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_7_5_X IBs (tests are also fine) and once validation in the development release cycle CMSSW_7_6_X is complete. This pull request requires discussion in the ORP meeting before it's merged. @slava77, @davidlange6, @Degano, @smuzaffar