asyncmy integration broken

[henadzit]

Describe the bug
Looks like asyncmy integration is broken. The errors module of asyncmy is not available but there might be other issues. It's quite unfortunate because we suggest asyncmy as a default option for MySQL in the docs.

To Reproduce
Replace aiomysql in the deps command in Makefile with asyncmy and run TORTOISE_MYSQL_PASS=123456 make test_mysql.

Expected behavior

• asyncmy integration should be working
• We should have a test suite running against asyncmy, at the moment we only run tests with aiomysql

[waketzheng]

Agree. And we should add asyncmy integration test to ci:

       - name: Run ci
         run: make ci
+      - name: Test asyncmy integration
+        run: |
+          poetry run pip install asyncmy
+          make test_mysql
+          make test_mysql_myisam  # I don't known whether this is required
       - name: Test FastAPI Example
         run: |