In 9c132a5f we replaced "buf" with a pointer and replaced
one instance of snprintf with asprintf -- but there was still one
snprintf left over, being crashy.

Fixes bug 29967; bug not in any released Tor. This is CID 1444262.

After this fix, we have no more unchecked mkdir() calls.

Bug 29939; CID 144254. Bugfix on 0.2.7.2-alpha.

This can't actually result in a null pointer dereference, since
pub_excl and sub_excl are only set when the corresponding smartlists
are nonempty.  But coverity isn't smart enough to figure that out,
and we shouldn't really be depending on it.

Bug 29938; CID 1444257.  Bug not in any released Tor.

For scripts that work with python2, use /usr/bin/python.
Otherwise, use /usr/bin/env python3.

Fixes bug 29913; bugfix on 0.2.5.3-alpha.

(main.c is a bit better, but shutdown.c is ugly)

Having the numbers in those messages makes some of the unit test
unstable, by causing them to depend on the initialization order of
the naming objects.

python3 scripts/maint/practracker/practracker.py --regen

Closes ticket 29912.

Since this is the first time that practracker has had a stable
output order, this diff will be larger than usual.