Test update to GitHub Actions (run against cfdm master)

[sadielbartholomew]

No description provided.

[sadielbartholomew]

Okay, first try has failed because it seems the relative directory structure of the job host VM isn't as I thought it was. The next commit I push in a moment tweaks the specified directories to change into before running pip install -e . to install development versions of cfdm/ and then cf-python/.

[sadielbartholomew]

Opening & closing to re-trigger.

[sadielbartholomew]

(Squashing & force-pushing to keep the commit history tidy & prevent having several correction commits.)

The run on cfdm master is working for all jobs except Python 3.5 ones where we are hitting a separate issue whereby netCDF4 isn't being installed successfully, I suspect this is due to it or one of its dependencies having dropped support for 3.5 since there is a deprecated warning given so 3.5 may soon be unsupported. Investigating, to confirm or otherwise, now.

[sadielbartholomew]

Yes, numpy now requires Python version 3.6 or greater (see https://github.com/numpy/numpy/blob/f1f1436b853f3855d75667ab4055cce06960fda9/setup.py#L464) hence the failure of the Python 3.5 jobs on the new 'install development...' step. So those failures are unrelated to the change to using cfdm master.

I will remove 3.5 from the run matrix for now, but @davidhassell we should discuss whether we should drop support for deprecated 3.5 ourselves (FYI it reaches "end of life" this month).

[sadielbartholomew]

I think this should be the last time I need to re-trigger, since the Python 3.X jobs for X != 5 all reached the 'run test suite' step for the previous try, so should pass without 3.5 jobs failing to cancel them like before. Let's see...

[sadielbartholomew]

Hmm, one spurious test failure that I can't recreate locally:

======================================================================
FAIL: test_Data_exp (test_Data.DataTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/runner/work/cf-python/cf-python/main/cf/test/test_Data.py", line 2830, in test_Data_exp
    self.assertTrue((d.array == c).all())
AssertionError: False is not true

----------------------------------------------------------------------
Ran 286 tests in 775.721s

FAILED (failures=1)

Trying once more in case it is a non-deterministic test.

[sadielbartholomew]

Okay the same test as above has failed again on the Python 3.8 job, so I will investigate that separately.

The run against cfdm master aspect is finalised, since the jobs run to completion even if they fail, so this is now good to merge.