Process examples in deterministic order

[bmwiedemann]

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Sort input file list
so that .pyc files in python-textX build in a reproducible way
in spite of indeterministic filesystem readdir order
and http://bugs.python.org/issue30461

See https://reproducible-builds.org/ for why this is good.

Might be related to https://bugs.python.org/issue34093

This PR was done while working on reproducible builds for openSUSE.

[goto40]

Thank you for your investigation and for the patch. Looks good from my side.

Maybe you could just add a newline (but we can also do that for you!) - to make our code style checker happy again / see travis outcome; the line is too long).

[bmwiedemann]

Added a linebreak+indent to make flake8 happy. My local flake8 still complained about unsorted imports, but I guess you do not care.

[igordejanovic]

@bmwiedemann Thanks.