portage.const: realpath(__file__.rstrip("co"))

With python2.x, __file__ may refer to the compiled bytcode file, but we
want to follow the symlink of the uncompile py file.
diff --git a/pym/portage/const.py b/pym/portage/const.py
index 93556a0..5e960d9 100644
--- a/pym/portage/const.py
+++ b/pym/portage/const.py
@@ -60,7 +60,7 @@
 # these variables are not used with target_root or config_root
 # NOTE: Use realpath(__file__) so that python module symlinks in site-packages
 # are followed back to the real location of the whole portage installation.
-PORTAGE_BASE_PATH        = os.path.join(os.sep, os.sep.join(os.path.realpath(__file__).split(os.sep)[:-3]))
+PORTAGE_BASE_PATH        = os.path.join(os.sep, os.sep.join(os.path.realpath(__file__.rstrip("co")).split(os.sep)[:-3]))
 PORTAGE_BIN_PATH         = PORTAGE_BASE_PATH + "/bin"
 PORTAGE_PYM_PATH         = PORTAGE_BASE_PATH + "/pym"
 LOCALE_DATA_PATH         = PORTAGE_BASE_PATH + "/locale"  # FIXME: not used