Fix travis builds
(Edited and updated)
Try various approaches to fix #1042 (closed) :
- Use an unique docker project name per build to test (see this)
- Use newer docker images (with a composer configuration adapted from SKA's)
- Avoid using Tango for
TaurusValueTest.test_text
(use a writable eval attribute instead of a tango one) - Allow failures for python2 tests in Travis (they hang/crash on exit of the pytest command, but typically the testsuite finishes without failures)