Check SqlState instead of error message

[e-tobi]

The PostgreSQL error messages are translated, so trying to match them against an english text might not work on different locales.

Please note, that here a 3 more places where the message text is evaluated, two of them only catching an Exception from reader.CloseAsync(). These lines of code are not not covered by any unit test and I couldn't figure out a sane way to trigger an exception there, so I left them untouched.

[mysticmind]

Just to be safe, I would suggest to change this to e.Message.Contains("does not exist") || e.SqlState == "3F000"?

[e-tobi]

There are A LOT of messages in PostgreSQL containing "does not exist":

https://github.com/postgres/postgres/blob/master/src/backend/po/de.po

I don't know which ones would make it to an exception, but my guess is "does not exist" is too unspecific.
Best solution would probably be to not rely on an exception at all and explicitly check for the schema existence.

[mysticmind]

@e-tobi I saw the changes what you have done to use PostgresErrorCodes, looks good to me as a fix. I have kick started the CI runs.