title: Docker python3.8 alpine python-ldab installation fails missing lber.h
body: <p>I am trying to pip install python-ldap in Docker but am missing lber.h. I need python-ldap because I am trying to implement an OS agnostic SSO for my application, following this for now and hoping it doesn't break the rest of my app <a href="https://code.tutsplus.com/tutorials/flask-authentication-with-ldap--cms-23101" rel="nofollow noreferrer">https://code.tutsplus.com/tutorials/flask-authentication-with-ldap--cms-23101</a></p>
  
  <p>I have tried </p>
  
  <p><code>RUN apk add libsasl2-dev libldap2-dev libssl-dev</code></p>
  
  <p>and </p>
  
  <p><code>RUN apk --no-cache add libsasl2-dev libldap2-dev libssl-dev</code></p>
  
  <p>but I get the following error:</p>
  
  <pre><code>ERROR: unsatisfiable constraints:
    libldap2-dev (missing):
      required by: world[libldap2-dev]
    libsasl2-dev (missing):
      required by: world[libsasl2-dev]
    libssl-dev (missing):
      required by: world[libssl-dev]
  </code></pre>
  
  <p>Having gone to <a href="https://pkgs.alpinelinux.org/packages?name=libldap2-dev&amp;branch=edge" rel="nofollow noreferrer">https://pkgs.alpinelinux.org/packages?name=libldap2-dev&amp;branch=edge</a> I feel that it is possible that these packages do indeed not exist within the alpine python image. Therefore, I tried substituting the installations with packages that exist in the above link, namely: openssl libsasl libldap 
  This didn't work either and had the same effect as not installing any of the packages i.e. the header missing error appeared:</p>
  
  <p>Modules/constants.h:7:10: fatal error: lber.h: No such file or directory</p>
  
  <pre><code> #include "lber.h"
            ^~~~~~~~
  compilation terminated.
  error: command 'gcc' failed with exit status 1
  </code></pre>
  
  <p>as a result of <code>/tmp/pip-install-doifa8k9/python-ldap/
  </code></p>
  
  <p>My Dockerfile:</p>
  
  <pre><code>    FROM python:3.8.0-alpine
  
      WORKDIR /home/flask
      ADD . /home/flask
  
      RUN apk --no-cache add --update --virtual .build-editdistance gcc g++ &amp;&amp; \
          apk --no-cache add libsasl libldap openssl &amp;&amp; \
          apk --no-cache add --update --virtual .libs libstdc++ &amp;&amp; \
          apk add linux-headers &amp;&amp; \
          apk add unixodbc-dev; 
  
      RUN rm -rf /var/cache/apk/* &amp;&amp; \
          pip install --upgrade pip &amp;&amp; \
          pip install --upgrade setuptools &amp;&amp; \
          pip install --no-cache-dir -Ur requirements.txt &amp;&amp; \
          apk del .build-editdistance;
  
      EXPOSE 5000
  </code></pre>