cache virtual environments and wheel files between stage

4 jobs for master in 1 minute and 18 seconds (queued for 1 second)
Name Stage Failure
test-3.5 Test There is an unknown failure, please try again
   afa2244..e4663aa  master     -> origin/master
Checking out e4663aaf as master...
Skipping Git submodules setup
Checking cache for default...
WARNING: venv2/include/python2.7: chmod venv2/include/python2.7: operation not permitted (suppressing repeats)
Successfully extracted cache
$ source venv3/bin/activate
bash: line 50: venv3/bin/activate: No such file or directory
ERROR: Job failed: exit status 1