tests/heredoctest.py

parsers: fix two leaks in index_ancestors

Both happy paths through this function leaked the returned list:

1) If the list was of size 0 or 1, it was retained an extra time and then
   returned.

2) If the list was passed to find_deepest, it was never released before
   exiting this function.

Both paths spotted by cpychecker.

import sys

globalvars = {}
lines = sys.stdin.readlines()
while lines:
    l = lines.pop(0)
    if l.startswith('SALT'):
        print(l[:-1])
    elif l.startswith('>>> '):
        snippet = l[4:]
        while lines and lines[0].startswith('... '):
            l = lines.pop(0)
            snippet += l[4:]
        c = compile(snippet, '<heredoc>', 'single')
        try:
            exec(c, globalvars)
        except Exception as inst:
            print(repr(inst))