[trivial] improved warning output for warnings that occur in doctests.  the now show the offending line of code.
Patches applied:

 * steve.alexander@canonical.com/launchpad--Menus--0--patch-43
   merge from rf

 * steve.alexander@canonical.com/launchpad--Menus--0--patch-44
   made warnings that occur in doctests get reported properly.

 * steve.alexander@canonical.com/launchpad--Menus--0--patch-45
   removed incorrect lineno from warning output about a doctest.

 * steve.alexander@canonical.com/launchpad--Menus--0--patch-46
   actually make the warning output show the line of doctest code causing the problem.