test-demandimport: ensure that relative imports are deferred

This adds a test not just at our local "top level" (the mercurial
package), but also one level deeper (mercurial.hgweb).

tests/test-demandimport.py

@@ -34,6 +34,11 b' print "util.system =", f(util.system)'
 print "util =", f(util)
 print "util.system =", f(util.system)
 
+from mercurial import hgweb
+print "hgweb =", f(hgweb)
+print "hgweb_mod =", f(hgweb.hgweb_mod)
+print "hgweb =", f(hgweb)
+
 import re as fred
 print "fred =", f(fred)
 

tests/test-demandimport.py.out

@@ -5,6 +5,9 b" util = <unloaded module 'util'>"
 util.system = <function system at 0x?>
 util = <module 'mercurial.util' from '?'>
 util.system = <function system at 0x?>
+hgweb = <unloaded module 'hgweb'>
+hgweb_mod = <unloaded module 'hgweb_mod'>
+hgweb = <module 'mercurial.hgweb' from '?'>
 fred = <unloaded module 're'>
 re = <unloaded module 'sys'>
 fred = <unloaded module 're'>