Dummy PR: demonstrate unit test failures

[rcomer]

🚀 Pull Request

Description

As raised on the Google Group, cftime v1.3 was released this week and is unforgiving about what kind of datetimes you can have. Iris tests now produce a raft of errors of the form

ValueError: invalid year provided in cftime.datetime(0, 0, 0, 0, 0, 0, 0, calendar='gregorian')

While demonstrating this locally, I saw a bunch of other failures that aren't obviously about cftime. So I figured the easiest way to raise this was to create a PR and let Travis show them!

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Consult Iris pull request check list

[rcomer]

I tried pinning cftime in my local requirements/ci/py37.yml. The resulting environment ran the tests with no failures or errors, so I guess cftime is the culprit for all the issues.

[rcomer]

It seems that, at cftime 1.3 you can still specify a zero datetime without a calendar using e.g.

cftime.datetime(0,0,0, calendar=None)

[rcomer]

Really not obvious how a flipped pressure coordinate would be caused by cftime.... 😕

@ -187,4 +187,4 @@
-        <dimCoord id="6eef7051" long_name="pressure" points="[0.1, 0.2, 0.3, 0.5, 0.7, 1.0, 2.0, 3.0, 5.0,
-		7.0, 10.0, 20.0, 30.0, 50.0, 70.0, 100.0, 150.0,
-		200.0, 250.0, 300.0, 400.0, 500.0, 600.0, 700.0,
-		850.0, 925.0, 950.0, 1000.0]" shape="(28,)" units="Unit('hPa')" value_type="float32"/>
+        <dimCoord id="6eef7051" long_name="pressure" points="[1000.0, 950.0, 925.0, 850.0, 700.0, 600.0,
+		500.0, 400.0, 300.0, 250.0, 200.0, 150.0, 100.0,
+		70.0, 50.0, 30.0, 20.0, 10.0, 7.0, 5.0, 3.0,
+		2.0, 1.0, 0.7, 0.5, 0.3, 0.2, 0.1]" shape="(28,)" units="Unit('hPa')" value_type="float32"/>

https://travis-ci.org/github/SciTools/iris/jobs/744701405#L26923-L26931

[bjlittle]

@rcomer We've already pin back cftime<1.3.0 and will be investigating this failure.

Do you still need this PR? Or happy to close? 🛩️

[rcomer]

Happy to close