Bump SQLAlchemy dependency version

[rfk]

From IRC:

max-m> By the way, the required version of SQLAlchemy could need a bump, because 1.1.5 is incompatible with MySQL 8. I bumped it to 1.1.18 in my installation, did not try the 1.2 branch.
03:59 
<•tcsc> rfkelly (maybe bobm?) ^
04:00 
<•bobm> Seems to work with MariaDB 10.x, but might be an issue.  We're okay for now.
04:01 
<•tcsc> might be something needing a fix in the docker repo though?
04:01 
— •tcsc doesn't really know
04:03 
<max-m> "'@@tx_isolation' is deprecated and will be removed in a future release. Please use '@@transaction_isolation' instead" MySQL 8 killed tx_isolation, newer verions of SQLAlchemy switched to the new name for MySQL 8.