nodetree: simplify a conditionnal in shortesthexnodeidprefix instead of try to catch some attribute error, we could just nicely look if the attribute will be available. This make the code simpler to follow and less error prone since we no longer rely on a wider attribute catching. Differential Revision: https://phab.mercurial-scm.org/D7651

config: close file even if we fail to read it If we get an exception from cfg.read(), we would not close the file before this patch. This patch uses a context manager to make sure we close it. Differential Revision: https://phab.mercurial-scm.org/D7626