cryptography >= 1.3.4 build sphinx docs

when you find following erros to build sphinx 1.5 documentation using .rst files.
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i was find these errors about cryptography must be high than 1.3.4 for build kivy docs on ubuntu 16.04 lts

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THIS ISSUE IS SOLVED WITH DEBIAN UBUNTU PACKAGE LIBSSL-DEV
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apt-get install libssl-dev

this solve requirement for build kivy docs on ubuntu 16.04 lts 64bits.

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mkdir -p build/html build/doctrees
sphinx-build -b html -d build/doctrees  -Q sources build/html
/usr/local/lib/python2.7/dist-packages/kivy/__init__.pyc

Exception occurred:
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 857, in resolve
    raise VersionConflict(dist, req).with_context(dependent_req)
ContextualVersionConflict: (cryptography 1.2.3 (/usr/lib/python2.7/dist-packages), Requirement.parse('cryptography>=1.3.4; extra == "security"'), set(['requests']))
The full traceback has been saved in /tmp/sphinx-err-ZCLTW3.log, if you want to report the issue to the developers.
Please also report this if it was a user error, so that a better error message can be provided next time.
A bug report can be filed in the tracker at <https://github.com/sphinx-doc/sphinx/issues>. Thanks!
Makefile:80: recipe for target 'html' failed
make: *** [html] Error 1