Revert "Make zip_plugin_files.py Python 3 compatible (bazelbuild/inte…

…llij PR import bazelbuild#978)"

This reverts commit 30d5f1e.

build_defs/zip_plugin_files.py

@@ -6,10 +6,6 @@
 import stat
 import zipfile
 
-# Keep this script executable from python2 in the host configuration.
-# Python2's open() does not have the "encoding" parameter.
-from io import open  # pylint: disable=redefined-builtin,g-bad-import-order,g-importing-member
-
 try:
   from itertools import izip  # pylint: disable=g-importing-member,g-import-not-at-top
 except ImportError:
@@ -32,7 +28,7 @@ def main():
   args = parser.parse_args()
   with zipfile.ZipFile(args.output, "w") as outfile:
     for exec_path, zip_path in pairwise(args.files_to_zip):
-      with open(exec_path, mode="rb") as input_file:
+      with open(exec_path) as input_file:
         zipinfo = zipfile.ZipInfo(zip_path, (2000, 1, 1, 0, 0, 0))
         filemode = stat.S_IMODE(os.fstat(input_file.fileno()).st_mode)
         zipinfo.external_attr = filemode << 16