Better formatting for config errors from modules (#8874)

The idea is that the parse_config method of extension modules can raise either a ConfigError or a JsonValidationError,
and it will be magically turned into a legible error message. There's a few components to it:

* Separating the "path" and the "message" parts of a ConfigError, so that we can fiddle with the path bit to turn it
   into an absolute path.
* Generally improving the way ConfigErrors get printed.
* Passing in the config path to load_module so that it can wrap any exceptions that get caught appropriately.

1 files changed, 1 insertions, 0 deletions

diff --git a/changelog.d/8874.feature b/changelog.d/8874.feature
new file mode 100644
index 0000000000..720665ecac
--- /dev/null
+++ b/changelog.d/8874.feature
@@ -0,0 +1 @@
+Improve the error messages printed as a result of configuration problems for extension modules.