Test support for date/datetime/time fields

[snorfalorpagus]

#540 got me looking at the support for date/datetime/time fields. It's a little complicated, with different drivers having different levels of support and behaviours. I've added some tests to illustrate the current behaviour. I don't think anything needs to change, except that we should raise a more useful error when trying to create a time-type field in an ESRI Shapefile, which currently raises an unexpected KeyError.

[coveralls]

Coverage remained the same at 84.065% when pulling 8acc147 on snorfalorpagus:datetime_tests into 35bdccb on Toblerity:master.

[coveralls]

Coverage remained the same at 84.065% when pulling 8acc147 on snorfalorpagus:datetime_tests into 35bdccb on Toblerity:master.

[coveralls]

Coverage increased (+0.3%) to 84.07% when pulling e2b84b4 on snorfalorpagus:datetime_tests into f3ce335 on Toblerity:master.

[snorfalorpagus]

Apparently GPKG support for datetime is in GDAL 2.x only. Need to update test further.

[snorfalorpagus]

This is an absolute rabbit hole! There are more exceptions than rules, with different behaviour between GDAL 1/2 and different formats. I think we should be raising warnings for some of these differences (silent type conversions, dropping times from dates, etc). I think the test needs reformatting also as with all the exceptions it's spaghetti. I'll keep working on this.

[sgillies]

@snorfalorpagus sorry for the review backlog! I'll try to get to them tomorrow. I see that we have an unresolved dependency on Windows.

[snorfalorpagus]

sorry for the review backlog! I'll try to get to them tomorrow. I see that we have an unresolved dependency on Windows.

No problem! I created #593 for the dependency issue.

The approach I've taken here is to raise a DriverSupportError if GDAL would do something unexpected (e.g. writing a date when a datetime was asked for), or a warning if the output is only mildly unusual (e.g. a non-standard date format).

[sgillies]

Wow, I'm baffled by the failure on Appveyor. The click-plugins project hasn't changed in a long time and we used to pass the tests with pip 10.0.1. I'm stumped for now.