building of lxml version 4.5.2 fails

[juk-stata]

I run in this error when trying to test the repo on Docker Play. Please follow these steps to reproduce

1. Got to https://labs.play-with-docker.com/
2. Sign in with your Docker Hub Account (you may have to create one first)
3. start a new instance
4. type git clone https://github.com/bartdegoede/python-searchengine.git (you can copy paste using Shift + Insert)
5. cd to newly created directory
6. create a venv using python3 -m venv .venv
7. activate venv: source .venv/bin/activate
8. install requirements: pip install -r requirements.txt

It will output the following error:

It's possible to install lxml manually using pip install lxml before step 8. But this has no effect

[rkdharun]

You can just install the latest lxml and everything works fine

[bartdegoede]

Fixed in #14