gnu: Python: disable failing tests on MIPS64.

* gnu/packages/patches/python-fix-tests.patch: disable two failing tests on
  MIPS64.

gnu: Python: disable test_wait_result() as it fails on some setups

* gnu/packages/patches/python-fix-tests.patch: disable a failing test.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

Merge branch 'core-updates'

gnu: Enable tests in Python 3.

* gnu/packages/python.scm: enable tests for Python 3
* gnu/packages/python-fix-tests.patch: New file.
* gnu/packages/gnu-system.am (dist_patch_DATA): add it.