Better error message for bad SequencePlaceholder

[Dr15Jones]

If a SequencePlaceholder is referring to an object of a type which is
not allowed on a Sequence (e.g. EDAlias) we now issue a useful exception
message.

[cmsbuild]

A new Pull Request was created by @Dr15Jones (Chris Jones) for CMSSW_7_5_X.

Better error message for bad SequencePlaceholder

It involves the following packages:

FWCore/ParameterSet

@cmsbuild, @Dr15Jones, @ktf, @nclopezo can you please review it and eventually sign? Thanks.
@Martin-Grunewald, @wddgit, @wmtan this is something you requested to watch as well.
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@nclopezo you are the release manager for this.
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[Dr15Jones]

please test

[Dr15Jones]

+1

[cmsbuild]

The tests are being triggered in jenkins.

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_7_5_X IBs unless changes or unless it breaks tests. This pull request requires discussion in the ORP meeting before it's merged. @davidlange6, @nclopezo, @ktf, @smuzaffar

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_7_5_X IBs unless changes or unless it breaks tests. This pull request requires discussion in the ORP meeting before it's merged. @davidlange6, @nclopezo, @ktf, @smuzaffar

[cmsbuild]

+1
Tested at: 6cf94d1
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-8827/4337/summary.html

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_7_5_X IBs unless changes (tests are also fine). This pull request requires discussion in the ORP meeting before it's merged. @davidlange6, @nclopezo, @ktf, @smuzaffar

[davidlange6]

+1

[cmsbuild]

Comparison is ready
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-8827/4337/summary.html

The workflows 140.53 have different files in step1_dasquery.log than the ones found in the baseline. You may want to check and retrigger the tests if necessary. You can check it in the "files" directory in the results of the comparisons