Add deprecation warning in PropertyProxy

If a property contains [[deprecated]] in its doc string, print a deprecation warning on setting the property value.

Example:

# WARNING: Property A1.ErrorMax is deprecated:  [[deprecated]] max number of errors [Algorithm] 

• [2018-03-14 15:13] Validation started with lhcb-gaudi-merge#448
• [2018-03-15 00:05] Validation started with lhcb-gaudi-head-py3#93
• [2018-03-15 00:08] Validation started with lhcb-tdr-test#89
• [2018-03-15 00:20] Validation started with lhcb-gaudi-head#1799

approved this merge request

@fwinkl, thanks a lot for this. I wanted to have it sine I introduced the '[[deprecated]]' convention for properties doc strings.

assigned to @clemenci

changed milestone to %v30r2

added code cleanup configuration labels

merged

mentioned in commit 38d044e2

It would have been nice, before merging this, to check the LHCb nightlies. The deprecation warning appears 1863 times in the Brunel build, see https://lhcb-nightlies.cern.ch/logs/build/nightly/lhcb-gaudi-head/1799/x86_64-slc6-gcc62-opt/Brunel/ (similarly https://lhcb-nightlies.cern.ch/logs/build/nightly/lhcb-gaudi-head/1799/x86_64-slc6-gcc62-opt/DaVinci/ and https://lhcb-nightlies.cern.ch/logs/build/nightly/lhcb-gaudi-head/1799/x86_64-slc6-gcc62-opt/Moore/)

While I agree that this MR goes in the right direction, I think it's unacceptable to introduce it one day and merge it the next, without giving users a chance to update their code. So, I request that this MR is reverted until we have had a chance to make the necessary changes.

Looking at the warnings @cattanem points out: do we really want to deprecate ExtraInputs? I was under the impression that was (ab/re)used to declare a (pseudo-data) dependency on the conditions lock... If ExtraInputs is removed, how should that be handled? (or am I mis-remembering?)

mentioned in merge request !639 (merged)

eventually we want to deprecate ExtraInputs and ExtraOutputs, but I think we're a long way from that.

mentioned in merge request !641 (merged)