Assume the raw environ is always declared. (GH-8707)

posixmodule.c always declares environ, so don't bother catching a NameError in os.py.

Lib/os.py

@@ -525,12 +525,6 @@ if {open, stat} <= supports_dir_fd and {scandir, stat} <= supports_fd:
 
     __all__.append("fwalk")
 
-# Make sure os.environ exists, at least
-try:
-    environ
-except NameError:
-    environ = {}
-
 def execl(file, *args):
     """execl(file, *args)