[PATCH 1 of 2] dispatch: move part of callcatch to scmutil

[Yuya Nishihara]

On Thu, 24 Nov 2016 13:39:25 +0000, Jun Wu wrote:
> Excerpts from Yuya Nishihara's message of 2016-11-24 22:28:28 +0900:
> > This seems better belonging to the high-level callcatch(), but anyway it looks
> > like a moot. If C extensions aren't compiled at all, ImportError would be
> > raised earlier.
> 
> demandimport could be a source of (surprising) ImportErrors with 3rd-party
> code. Like hgsubversion imports svn binding, while the binding does not
> exist.

Yeah, but "hg" calls util.setbinary(), where ImportError would be raised if
osutil.so is missing.