demandimport: update obsolete comment

demandimport: add support for PyPy PyPy's implementation of __import__ differs subtly from that of CPython. If invoked without a name or fromlist, it throws an ImportError, whereas CPython returns a reference to the level-appropriate importing package. Here, we achieve the same behaviour by hand.

test-demandimport: ensure that relative imports are deferred This adds a test not just at our local "top level" (the mercurial package), but also one level deeper (mercurial.hgweb).

histedit: don't bother with cPickle, demand-load pickle We're unlikely to ever need the pickle module, so there's no good reason to force loading of its faster cousin.

merge with stable

crecord: stop raising error.Abort if curses is not found (issue5008) On some servers, python curses support is disabled. This patch not only fixes that but provides a fallback on other machines (e.g. Windows) when curses is not found. The previous code was actually flawed logic and relied on wcurses throwing an ImportError which demandimport wouldn't throw. So, this patch also fixes that problem.

cmdutil: use crecordmod.checkcurses Instead of blindly trusting the user's experimental.crecord, we use checkcurses to abstract that logic so that we can handle the case where python was not built with curses.

crecord: ensure that curses is False if not imported This provides no functional change but makes the next two patches easier to review.

crecord: add helper function to determine if we should use curses To fix issue5008 properly, we need a helper function to determine if curses is imported and also if the user has enabled the experimental flag.

crecord: use try/except for import of curses Not only does this improve fragility with 'if os.name == ...' it will help future patches enable the behavior to fallback to use plain record when curses is unavailable (e.g. python compiled without curses support).