util: handle fileno() on Python 3 throwing io.UnsupportedOperation
Fortunately, the exception exists on Python 2 so we don't have to do
something weirder than this.
Differential Revision: https://phab.mercurial-scm.org/D2450
Mercurial
=========
Mercurial is a fast, easy to use, distributed revision control tool
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Basic install::
$ make # see install targets
$ make install # do a system-wide install
$ hg debuginstall # sanity-check setup
$ hg # see help
Running without installing::
$ make local # build for inplace usage
$ ./hg --version # should show the latest version
See https://mercurial-scm.org/ for detailed installation
instructions, platform-specific notes, and Mercurial user information.