cppcms_tmpl_cc is incompatible with python3

[masaoliou]

[ 13%] Built target booster
[ 27%] Built target cppcms
[ 28%] Built target forwarder_test
[ 29%] Built target filter_test
[ 29%] Built target base64_test
[ 29%] Generating tc_skin_b.cpp
Traceback (most recent call last):
  File "/tmp/cppcms/bin/cppcms_tmpl_cc", line 14, in <module>
    import StringIO
ModuleNotFoundError: No module named 'StringIO'
make[2]: *** [CMakeFiles/tc_skin_b.dir/build.make:82: tc_skin_b.cpp] Error 1
make[1]: *** [CMakeFiles/Makefile2:387: CMakeFiles/tc_skin_b.dir/all] Error 2
make: *** [Makefile:182: all] Error 2

[artyom-beilis]

It is already fixed in both master (1.2.x branch) and it is fixed in beta 2.0/cpp11 branch

I suggest take beta 2.0 (it is as stable as 1.2 but comes with better c++11 support) or if you prefer take master for git.