This allows us to write doctests depending on a ui object, but not on global
configs.
ui.load() is a class method so we can do wsgiui.load(). All ui() calls but
for doctests are replaced with ui.load(). Some of them could be changed to
not load configs later.
Since (b) is banned, we should do the same for (a) for consistency.
a) from mercurial import hg
from mercurial.i18n import _
b) from . import hg
from .i18n import _
