title: Docker build fails to install pyrfy
body: <p>I am trying to build an image with docker containing some pretty simple packages.
  Here's the requirements file:</p>
  <pre><code>autoimpute==0.12.2
  numpy==1.19.2
  fuzzywuzzy==0.18.0
  pymongo==3.11.4
  boto3==1.18.65
  pandas==1.1.3
  pytest==0.0.0
  scikit_learn==1.0
  </code></pre>
  <p>Dockerfile:</p>
  <pre><code>FROM public.ecr.aws/lambda/python:3.8
  
  COPY app.py requirements.txt ./
  COPY data data/
  COPY models models/
  COPY models_autoML models_autoML/
  
  RUN apt install swig
  RUN python3.8 -m pip install -r requirements.txt -t .
  
  COPY dsci1.py ./
  
  # Command can be overwritten by providing a different command in the template directly.
  CMD [&quot;app.lambda_handler&quot;]
  </code></pre>
  <p>I get the following error, which is weird since I pulled a project from another collaborator and it is supposed to work. Why is it failing, and what can I do to fix it?</p>
  <pre><code>#10 18.88   error: subprocess-exited-with-error
  #10 18.88
  #10 18.88   × Running setup.py install for pyrfr did not run successfully.
  #10 18.88   │ exit code: 1
  #10 18.88   ╰─&gt; [7 lines of output]
  #10 18.88       running install
  #10 18.88       running build_ext
  #10 18.88       building 'pyrfr._regression' extension
  #10 18.88       swigging pyrfr/regression.i to pyrfr/regression_wrap.cpp
  #10 18.88       swig -python -c++ -modern -py3 -features nondynamic -I./include -o pyrfr/regression_wrap.cpp pyrfr/regression.i
  #10 18.88       unable to execute 'swig': No such file or directory
  #10 18.88       error: command 'swig' failed with exit status 1
  #10 18.88       [end of output]
  #10 18.88
  #10 18.88   note: This error originates from a subprocess, and is likely not a problem with pip.
  #10 18.88 error: legacy-install-failure
  #10 18.88
  #10 18.88 × Encountered error while trying to install package.
  #10 18.88 ╰─&gt; pyrfr
  </code></pre>