cleanup in html template + tidylib ...

* few small cleanup in html template (avoid empty tbody, put id between
quotes)
* switch to tidylib to validate the html instead of the previous hack
calling an external service (https://html5.validator.nu/)
* remove the previous validator script
* add exception for tidylib on empty <span> (these are required by
bootstrap)

remove debug print

fix html validator test for python 3

force the groups in flatten roles to be sorted ...

* sorting the groups helps debuggability and also permits testing
that doesn't rely on python ordering (which is different between 2 and
3).

fix test and exception handling in code ...

With python 2 it was possible to do exception[0][...] to recover
details about an exception.
It's no longer authorized with python 3.
Now, we must do something like exception.args or exception.urls.
fortunately this syntax also works with python 2.
So we use it for both.

remove deprecation warning for html escape ...

in python 2, (html) escape is part of the cgi module
in python 3, it's part of the html module

we now do a conditional import depending on the version, and name the
function html_escape.

fix behavior of get_attributes() ...

* make sure it returns an ordered list in both python 2 and python 3

add some python 3 support in the LDAP and AD backends ...

python-ldap talks in bytes,
as the rest of ldapcherry talks in unicode utf-8:
* everything passed to python-ldap must be converted to bytes
* everything coming from python-ldap must be converted to unicode

The previous statement was true for python-ldap < version 3.X.
With versions > 3.0.0 and python 3, it gets tricky,
some parts of python-ldap takes string, specially the filters/escaper.

so we have now:
*_byte_p2 (unicode -> bytes conversion for python 2)
*_byte_p3 (unicode -> bytes conversion for python 3)
*_byte_p23 (unicode -> bytes conversion for python AND 3)

disable ppolicy in samba test deployment

limit cherrypy to < 18.0.0 in setup.py ...

cherrypy dropped support for python2 with 18.0.0, 17.X is the last
version usable with python 2.

pep8

* support for python-ldap 2 and 3 ...

* python-ldap 3 is slightly different than 2 on how it handles modify
the modified attributes used to be transmitted as a dict, now it should
be transmitted as a list of dict)

changelog

better log+fix in conf checking + fix in ppolicy handler ...

* log where the backend is declared (role or attribute) when
inconsistency with main .ini file
* fix check of configuration, only role file was checked 2 times instead
on checking role one time and attribute one time
* <dict>.keys() seems to have a different behavior between 2 (return
"list") and 3 (return "dict_keys"), casting to "list" to avoid that.

pep8

better handling of the str/byte mess for python3 ...

* add dedicated methods for python 3 in handling of bytearrays/strings
* using them to compare attributes checks in AD backend

switch to explicit bytearray for checking missing params

trying to fix samba/AD setup

cleanup in travis file

adding another samba package in test env

adding another dependency for the samba/ad test

remove python3 test env for el7 and stretch (no python3-ldap lib anyway)

fixing the test env deploy script + small fix in unit tests

fix pip install

add requirements files for simulating RHEL 7 and Debian 9

pep 8

remove scripts from pycodestyle

porting the tests over to python3

pep8

adding an update as the first step of the deploy script