No module named 'PIL

When installing on my RaspberryPi, I get this error when running pip install -r requirements.txt

ERROR: Command errored out with exit status 1:
     command: /opt/ivatar/ivatar/.virtualenv/bin/python3 -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'/tmp/pip-req-build-9qiryzy2/setup.py'"'"'; __file__='"'"'/tmp/pip-req-build-9qiryzy2/setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' egg_info --egg-base /tmp/pip-pip-egg-info-ofy7p5ap
         cwd: /tmp/pip-req-build-9qiryzy2/
    Complete output (7 lines):
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "/tmp/pip-req-build-9qiryzy2/setup.py", line 4, in <module>
        import Identicon
      File "/tmp/pip-req-build-9qiryzy2/Identicon/__init__.py", line 6, in <module>
        from PIL import Image, ImageDraw
    ModuleNotFoundError: No module named 'PIL'
    ----------------------------------------
WARNING: Discarding git+https://github.com/flavono123/identicon.git. Command errored out with exit status 1: python setup.py egg_info Check the logs for full command output.
ERROR: Command errored out with exit status 1: python setup.py egg_info Check the logs for full command output.