Heroku: "directory exists" error after changing requirements.txt
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For one of the libraries I use, I'm trying to switch from a mercurial repository to git. Unfortunately when I tried to push the project with new requirements.txt file, I get this:

    Obtaining django-storages from git+https://github.com/richleland/django-storages/#egg=django_storages (from -r requirements.txt (line 2))
      Directory /tmp/build_3lujzy9ddaetm/.heroku/src/django-storages already exists, and is not a git clone.
      The plan is to install the git repository https://github.com/richleland/django-storages/
    What to do?  (i)gnore, (w)ipe, (b)ackup Exception:
    Traceback (most recent call last):
    ...
    EOFError: EOF when reading a line

Forcing the push (-f) ends with the same message. How do I make this work?