demandimport: prefer loaded module over package attribute (
issue5617)
In general, the attribute of the same name is overwritten by executing an
import statement.
import a.b
print(a.b.c) # 'c' of a/b/__init__.py
from a.b.c import d
print(a.b.c) # a/b/c.py
However, this appears not true for the scenario described in the test case,
and surprisingly, "from a.b.c import d" works even if "a.b.c" is not a module.
This patch works around the problem by taking the right module from sys.modules
if available.
demandimport: drop hack for old Pythons which had no level argument
_import() was added by
868282fa29d8, but it is identical to _origimport()
now.