test_compile_extension_module always use the same Instant cache

[Johannes Ring]

The unit test test_compile_extension_module in test/unit/python/jit/test_jit.py is always using the same Instant cache, even if for instance the DOLFIN version number is changed. This test creates two extension modules, one with module name mypetscmodule and one with no (empty) module name. The one with no module name will be given a unique module name based on the hex of the DOLFIN version number (among other things), while the mypetscmodule module will always have the same name even when the version number changes. This has caused the problems we have seen lately on Bamboo with many failed and hung builds. How can we change this test to fix this problem? Can we give it another module name which includes the DOLFIN version number somehow instead of just calling it mypetscmodule?

[Jan Blechta]

What about removing module_name kwarg from compile_extension_module? Does anybody need it?

[Prof Garth Wells]

As a quick fix we could append (manually) the version number.

[Jan Blechta]

Note that a real fix would be to hash DOLFIN (and eventually other) includes. See #372.

[Prof Garth Wells]

Duplicate of #372.