Confirm support for GDAL 2.3

[Tim Graham]

I see a number of test failures with GDAL 2.3 (attached) but as in #28257, it might merely be a problem on my machine.

[Claude Paroz]

I just compiled a fresh 2.3 and obtained those 2 failures only:

======================================================================
FAIL: test_poly_multi (gis_tests.inspectapp.tests.OGRInspectTest)
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Traceback (most recent call last):
  File "/home/claude/checkouts/django-git/tests/gis_tests/inspectapp/tests.py", line 91, in test_poly_multi
    self.assertIn('geom = models.MultiLineStringField(srid=-1)', model_def)
AssertionError: 'geom = models.MultiLineStringField(srid=-1)' not found in '# This is an auto-generated Django model module created by ogrinspect.\nfrom django.contrib.gis.db import models\n\n\nclass MyModel(models.Model):\n    laenge = models.FloatField()\n    breite = models.FloatField()\n    nummer = models.BigIntegerField()\n    geom = models.MultiLineStringField(srid=31253)'

======================================================================
FAIL: test05_geometries (gis_tests.gdal_tests.test_ds.DataSourceTest)
Testing Geometries from Data Source Features.
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Traceback (most recent call last):
  File "/home/claude/checkouts/django-git/tests/gis_tests/gdal_tests/test_ds.py", line 230, in test05_geometries
    self.assertIsNotNone(re.match(wgs_84_wkt_regex, g.srs.wkt))
AssertionError: unexpectedly None

[Claude Paroz]

This ​PR is solving the WGS 84 regex. I have no idea for the other failure, how GDAL can find a 31253 srid.
Note also that we should drop official support for GDAL 1.9 and 1.10 at least.

[Claude Paroz <claude@…>]

In 86988dd:

Refs #29483 -- Relaxed WGS 84 check regex

With GDAL 2.3, the exact string changed again.

[Claude Paroz <claude@…>]

In 69e2d173:

[2.1.x] Refs #29483 -- Relaxed WGS 84 check regex

With GDAL 2.3, the exact string changed again.
Backport of 86988dd890671aa8935f86eab2bbe22ad917db70 from master.

[Tim Graham]

"EPSG:31253 Projected coordinate system for Austria east of 14°50'E of Greenwich (32°30'E of Ferro)." seems to make sense given a mention of Austria in the ​gas_leitung test data file.

​PR

[Claude Paroz]

Ahhh.. I didn't notice that the second part of the test was using gas_leistung.shp. Makes sense now.

[GitHub <noreply@…>]

In 9e4f26bb:

Fixed #29483 -- Confirmed support for GDAL 2.3.