title: Why pipenv shell does not get recognized
body: <p>I have a Dockerfile with the following content: </p>
  
  <pre><code>FROM ubuntu:bionic AS os
  RUN apt-get update \
      &amp;&amp; apt-get install -y git \
      &amp;&amp; apt-get install -y python3.7 python3-pip \
      &amp;&amp; cd /usr/local/bin \
      &amp;&amp; ln -s /usr/bin/python3.7 python \
      &amp;&amp; pip3 install --upgrade pip \
      &amp;&amp; pip install pipenv \
      &amp;&amp; apt-get install -y curl \ 
      &amp;&amp; curl -sL https://deb.nodesource.com/setup_13.x | bash - \
      &amp;&amp; apt-get install -y nodejs \
      &amp;&amp; curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | apt-key add - \
      &amp;&amp; echo "deb https://dl.yarnpkg.com/debian/ stable main" | tee /etc/apt/sources.list.d/yarn.list \
      &amp;&amp; apt update \
      &amp;&amp; apt install yarn
  
  RUN git clone https://gitlab.com/silentdata/cdtc-identity-service.git
  ENV LANG=C.UTF-8
  ENV LC_ALL=C.UTF-8
  WORKDIR /cdtc-identity-service
  RUN pipenv --python 3.7
  RUN pipenv install
  RUN pipenv shell
  </code></pre>
  
  <p>During the image build process, I've got:</p>
  
  <pre><code>Step 9/9 : RUN pipenv shell
   ---&gt; Running in a087d2296eb8
  Launching subshell in virtual environment…
  Traceback (most recent call last):
    File "/usr/local/bin/pipenv", line 8, in &lt;module&gt;
      sys.exit(cli())
    File "/usr/local/lib/python3.6/dist-packages/pipenv/vendor/click/core.py", line 764, in __call__
      return self.main(*args, **kwargs)
    File "/usr/local/lib/python3.6/dist-packages/pipenv/vendor/click/core.py", line 717, in main
      rv = self.invoke(ctx)
    File "/usr/local/lib/python3.6/dist-packages/pipenv/vendor/click/core.py", line 1137, in invoke
      return _process_result(sub_ctx.command.invoke(sub_ctx))
    File "/usr/local/lib/python3.6/dist-packages/pipenv/vendor/click/core.py", line 956, in invoke
      return ctx.invoke(self.callback, **ctx.params)
    File "/usr/local/lib/python3.6/dist-packages/pipenv/vendor/click/core.py", line 555, in invoke
      return callback(*args, **kwargs)
    File "/usr/local/lib/python3.6/dist-packages/pipenv/vendor/click/decorators.py", line 64, in new_func
      return ctx.invoke(f, obj, *args, **kwargs)
    File "/usr/local/lib/python3.6/dist-packages/pipenv/vendor/click/core.py", line 555, in invoke
      return callback(*args, **kwargs)
    File "/usr/local/lib/python3.6/dist-packages/pipenv/cli/command.py", line 390, in shell
      pypi_mirror=state.pypi_mirror,
    File "/usr/local/lib/python3.6/dist-packages/pipenv/core.py", line 2184, in do_shell
      shell.fork_compat(*fork_args)
    File "/usr/local/lib/python3.6/dist-packages/pipenv/shells.py", line 121, in fork_compat
      c.interact(escape_character=None)
    File "/usr/local/lib/python3.6/dist-packages/pipenv/vendor/pexpect/pty_spawn.py", line 761, in interact
      mode = tty.tcgetattr(self.STDIN_FILENO)
  termios.error: (25, 'Inappropriate ioctl for device')
  </code></pre>
  
  <p>What am I doing wrong?</p>