I have just created a virtual environment on my machine (I am running on ubuntu 18.04 LTS). I have the python version of 3.6.7 and now I want to install mysqlclient into my virtual environment.
After I do pip install mysqlclient it didn't work, instead it gave me errors saying; 

Command "python.py egg_info" failed with error code 1 in /tmp/pip-install-zd21vfb3/mysqlclient/', and that the msql_config file is not found. 

My setup tools are all up to date.
mysqlclient has a dependency on the mysql client & dev packages being installed.  In order to fix this on ubuntu, you have to use apt-get to install a couple of mysql packages.
In your case, it looks like the missing mysql_config might be missing on your system.  You can fix that by installing libmysqlclient-dev on ubuntu bionic.
why 'pip install mysqlclient' not working in ubuntu 18.04 LTS