py3kcompat: drop unused export

py3kcompat: don't convert os.environ to bytes os.environ accepts str not bytes. Assigning bytes will result in a run-time error.

demandimport: pass proper level to __import__ in Python 3 demandimport was failing in Python 3 with a ValueError because __import__'s level=-1 has gone away (-1 means to try both relative and absolute imports and relative imports don't exist in Python 3). With this patch, demandimport still doesn't work in Python 3 (it fails when importing a non-package module).