title: 'No Space Left on Device' error when Pipenv tries to lock file
body: <p>I am new to Pipenv, having only installed it to run Sphero's SDK, and while trying to install additional modules, I came across this problem.  Pipenv would install the packages just fine, but then it would say that my Pipfile.lock was out of date.  It automatically started installing the newer file, then I get this: <code>Locking [dev-packages] dependencies... Locking [packages] dependencies... ✘ Locking Failed!  </code>
  It then gives me a long list of errors larger than my display, but at the end it says this: <code>OSError: [Errno 28] No space left on device</code>. What is wrong with my device?</p>