The libssl-dev is a hard dependency for mysqlclient package, otherwise `pip3 install mysqlclient` fails with
```
/usr/bin/ld: cannot find -lssl
/usr/bin/ld: cannot find -lcrypto
collect2: error: ld returned 1 exit status
error: command 'arm-linux-gnueabihf-gcc' failed with exit status 1
```
It should be documented as less experienced users won't be able to install mysqlclient on their machines