Remove deprecated code and declare 9.0 compatibility

I think we have to hold off until 8.7 is EOL for some of these?

Failing tests makes it hard to ensure that everything else still works on 8.7, I'd suggest to combine this with core_version_requirement: ^8.8 || ^9 and wait until @larowlan feels OK with no longer supporting 8.7.

Yeah either that or we have two branches, not fussed - if two branches unblocks people - so be it

Whether new branch or no, we need the version requirement, so needs work for that.

There's no need for that, removing drush8 support can be done later when support for D8 is removed entirely, no need to break sites that still use drush8 on D8.

I'd prefer to get commit first #2921377: When Drupal 8.6.0 is released, remove TermEntityNormalizer and tag a new release

So added 8.7.7 requirement to info file and hardened check in for exception message

+++ b/tests/src/Kernel/ExporterIntegrationTest.php
@@ -198,7 +198,7 @@ class ExporterIntegrationTest extends KernelTestBase {
-    $this->setExpectedException(\InvalidArgumentException::class);
+    $this->expectException(\InvalidArgumentException::class);

this method is deprecated in phpunit6 IIRC, so I thing it's good to go

FYI https://phpunit.de/getting-started/phpunit-5.html so since phpunit5 expectException is recommended method

Assigning to Lee to decide - at least clean-up of test is no longer blocker

+++ b/src/Exporter.php
@@ -231,7 +242,7 @@ class Exporter implements ExporterInterface {
-    file_prepare_directory($path, FILE_CREATE_DIRECTORY);

is deprecated in 8.7

Also needs to fix testing modules and schema in test

With #2921377 applied it passes tests on 9.0.x

And theme)

and it will need tuning of composer.json

Going to need a reroll and updating composer.json too as we already have the drupal/core require there.

Fixed remains

+++ b/default_content.info.yml
@@ -4,4 +4,4 @@ description: 'Imports default content when a module is enabled'
 dependencies:
-  - drupal:hal (>=8.6.x)
+  - drupal:hal (>=8.7.7)

I'd say we should remove the version from drupal:hal because it's covered with the line above and it's one thing less we'll need to update in the future.

Thanks, since this only requires 8.7 it's fine to commit now.