Merge branch 'protect_msgs' into 'master'

Protect messages in event loop

See merge request !1100
14 jobs for master in 31 minutes and 57 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #9150100
cvmfs
build:gcc8:opt

00:12:08

passed #9150102
cvmfs
build:gcc9:dbg

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passed #9150101
cvmfs
build:gcc9:opt

00:14:47

passed #9150103
cvmfs
build:gcc9:opt:python3

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passed #9150104
check-formatting

00:00:37

 
  Test
passed #9150105
check-copyright

00:01:04

passed #9150106
cvmfs
doxygen

00:03:49

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cvmfs
test:gcc8:opt

00:08:14

passed #9150109
cvmfs
test:gcc9:dbg

00:10:43

passed #9150108
cvmfs
test:gcc9:opt

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passed #9150110
cvmfs
test:gcc9:opt:python3

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passed #9150111
cvmfs
test_public_headers_build

00:03:03

passed #9150112
test-python3

00:01:07

 
  Deploy
passed #9150113
deploy-doxygen

00:00:43