AFAIK you cannot do what you require. You could wait for someone more experienced to reply, try OSMC which does not have the install restrictions, or look for a docker solution. Or try all of the them.
You can do anything through Docker.
LE is NOT designed to be anything but "Just enough OS for Kodi", As I mentioned before, try OSMC,
MySQLdb for python is available in entware. Too bad we don't have it in LE 
Yes too bad indeed
Too bad as well. 
So:
The hard way.
1. Install docker: Add-ons --> Install from repository --> LibreELEC Add-ons --> Services -- Docker.
Once finished: Login with ssh.
2. mkdir /storage/<Working Directory>
3. cd <Working Directory>
4. nano pip-requirements.txt
mysql-python
mysql-connector-python5. nano Dockerfile
FROM python:2
WORKDIR /storage/<Working directory>
COPY pip-requirements.txt ./
RUN pip install --no-cache-dir -r pip-requirements.txt
COPY . .
CMD [ "python", "/storage/<Working directory>/<Name of your script>.py" ]6. Now install docker python
docker pull python7. Now build the docker image
docker build -t <Name of your script>.py .8 ...... and if all goes well, run it
docker run -it --rm --name <What it is know as> <Name of your script>.py