ui: remove urllib2 from being imported early Before this change, urllib2 was brought in when constructing the ui object, and that added ~5ms on my Linux workstation to the hg startup time for every command, bringing the time for 'HGRCPATH=/dev/null hg root' from 46ms to 40ms. Now, we construct a single proxy object per initial ui creation (so that if the ui is copied they share the object), but defer the actual instantiation of it and the import of urllib2 until it's needed. # no-check-commit