Enable demandimport only in scripts, not in importable modules (issue605)
This way other applications can choose if and when they want this feature,
because it might be problematic if those applications rely on ImportError.
os = <unloaded module 'os'>
os.system = <built-in function system>
os = <module 'os' from '?'>
mercurial.version = <unloaded module 'version'>
mercurial.version.get_version = <function get_version at 0x?>
mercurial.version = <module 'mercurial.version' from '?'>
mercurial = <module 'mercurial' 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'>