view tests/test-demandimport.out @ 8311:e0eb03bfa5af

manpage build: fail early when xmlto is not available

When we try to build manpages with xmlto and sed, but xmlto is
missing fail at the xmlto stage.  Otherwise, one may run `cd doc;
make' and miss the warnings like:

  xmlto: not found
  sed: hg.1: No such file or directory

and end up with empty files installed as manpages.

os = <unloaded module 'os'>
os.system = <built-in function system>
os = <module 'os' from '?'>
util = <unloaded module 'util'>
util.system = <function system at 0x?>
util = <module 'mercurial.util' from '?'>
util.system = <function system at 0x?>
fred = <unloaded module 're'>
re = <unloaded module 'sys'>
fred = <unloaded module 're'>
fred.sub = <function sub at 0x?>
fred = <proxied module 're'>
re = <unloaded module 'sys'>
re.stdout = <open file '<stdout>', mode 'w' at 0x?>
re = <proxied module 'sys'>