util: Update style file->open for python3

Change-Id: Ibcce194b1905f0e7f29aa91fd0ff881ba879ad51
Signed-off-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/29068
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>

util/style/file_types.py

@@ -104,7 +104,7 @@ def lang_type(filename, firstline=None, openok=True):
     # if a first line was not provided but the file is ok to open,
     # grab the first line of the file.
     if firstline is None and openok:
-        handle = file(filename, 'r')
+        handle = open(filename, 'r')
         firstline = handle.readline()
         handle.close()
 
@@ -173,7 +173,7 @@ def update_file(dst, src, language, mutator):
             mode = 'r+'
         else:
             mode = 'r'
-        src = file(src, mode)
+        src = open(src, mode)
 
     orig_lines = []
 
@@ -196,7 +196,7 @@ def update_file(dst, src, language, mutator):
     elif isinstance(dst, str):
         # if we're not updating in place and a destination file name
         # was provided, create a file object
-        dst = file(dst, 'w')
+        dst = open(dst, 'w')
 
     for line in new_lines:
         dst.write(line)