NEW: databases/py-pymysql

This is a maintained pure-Python mysql/mariadb client library.
The new version of LibreNMS wants it (I can patch around that, but
it seems useful to have anyway). I chose not to force the optional
dependency on py-rsa because pulls in the fairly large (and not
pure-Python) py-cryptography.

OK to import?


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PyMySQL is a pure-Python MySQL client library, based on PEP 249.
Most public APIs are compatible with mysqlclient and MySQLdb.

If you would like to use "sha256_password" or "caching_sha2_password"
for authentication, you need to also install the ${MODPY_PY_PREFIX}rsa
package.
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