Users/developers have reported that our project has too many Python dependencies. This is related to things being overly complex.

Here is pde's attempt to characterize what our dependencies currently are:

1. Purely for certbot-auto and the things it needs to build, not for
   the python code itself (these no longer apply on recent OSes where we have packages):

   git
   gcc
   python-dev
   libffi-dev
   libssl-dev
   setuptools
   virtualenv

2. Essential OS packages
   python
   openssl

3. Semi-essential OS packages:
   dialog

4. Needed for specific plugins:

   python-psutil (standalone -- see what has bound :80 or :443) (now only "recommended")
   libaugeas0 (apache -- parse & edit conf files)
   python-augeas

5. Python dependencies:

   ConfigArgParse (for reading config files)
   configobj (for writing & reading renewal conf files)
   python-cryptography (>= 0.8)
   PyOpenSSL (>= 0.15) (>= 0.13)
   pythondialog
   ndg-httpsclient (for working around TLS insecurities in older Python versions)
   requests
   six

6. Python dependencies specifically related to time processing. It seems
   absurd that there are four of these:

   werkzeug
   pytz
   parsedatetime
   pyicu (needed by parsedatetime)
   pyrfc3339

7. Python dependencies for python-cryptography:
   idna
   enum34
   ipaddress
   cffi
   pycparser (build dep only, but affects letsencrypt-auto)
   pyasn1

8. These were used to define plugin interfaces. Not sure if that was wise,
   but it's probably annoying to third parties if we ditch them:

   zope.components
   zope.interface
   zope.event

9. Development and doc-building dependencies. For reasons I don't
   yet understand, pip always fetches some of these too:

   mock
   funcsigs (mock depends on this)
   pbr (mock depends on this)
   sphinxdocs