On each plugin initialization we create a separate python interpreter
which gets stored in the plugin_ctx. The main interpreter is
stored in py_ctx and is used for creating more interpreters (if more plugins
get loaded) and final python deinitialization.
The "traceback" module import and the ImportBlocker initialization was
moved, because it has to happen inside the plugin specific interpreters.
Adapted the default sudo_printf from sudoers plugin to be able to print
errors before plugin open() gets called. (This is used by the multiple io
plugin loading to display error for too much plugin load.)
Since this makes us always have a sudo_log, I have removed the logic about
whether it is available or not.
When calling validate() python function, TypeError exception was thrown
("argument list must be a tuple"), because the call does not have
arguments, and python does not accept empty tuple for execution. NULL
must be used instead, which was handled as argument construction failure
previously.
IO/Group/Policy Python API version is displayed instead of sudo version,
because that is not very meaningful in this context.
They are only displayed in verbose mode.
Example plugins express it more concrete that they are displaying their
version, not the API version.
