Brett Cannon wrote:
> 
> You can see a little discussion in http://bugs.python.org/issue14642, but it has been discussed elsewhere and the automatic rebuilding was preferred (but it is not a requirement to build as importlib.h is in hg).

An automatic rebuild is fine, but only as long as the local ./python
actually exists.

I was unaware of make rule, so did not run make to check things before
the checkin. As a result, the bootstrap module received a more recent
timestamp than importlib.h and this caused all the buildbots to
force a rebuild of importlib.h - which failed, since they didn't
have a built ./python at that stage.

I checked in a fix and added a warning to the bootstrap script.