travis CI fails with errors related to quadprog dependency

[m-jahn]

Travis CI recently throws errors for commits that have worked previously. The chnage must therefore come from a dependency that was updated. The error message is:

Error in dyn.load(file, DLLpath = DLLpath, ...) : 
  unable to load shared object '/home/travis/R/Library/quadprog/libs/quadprog.so':
  libRblas.so: cannot open shared object file: No such file or directory
Calls: <Anonymous> ... namespaceImport -> loadNamespace -> library.dynam -> dyn.load
Execution halted
ERROR: lazy loading failed for package ‘latticetools’
* removing ‘/tmp/RtmpQixtCX/Rinst3790614754c8/latticetools’

The error seems to come from quadprog, a dependency of directlabels package. However, quadprog itself has no other dependencies and should not need local installation of lipblas and liblapack on linux systems. But complains that a compiled C++ file is missing.

[m-jahn]

Note: the error does not show up locally with R version 3.6.3 (2020-02-29) while Travis CI uses R version 4.0.0 (2020-04-24).

[m-jahn]

The error disappeared after pushing a new (unrelated) commit and re-running Travis CI. Most likely a problem in one of the dependencies that was fixed already.