[PATCH v2] decodetree: Open files with encoding='utf-8'

[Philippe Mathieu-Daudé]

When decodetree.py was added in commit 568ae7efae7, QEMU was
using Python 2 which happily reads UTF-8 files in text mode.
Python 3 requires either UTF-8 locale or an explicit encoding
passed to open(). Now that Python 3 is required, explicit
UTF-8 encoding for decodetree source files.

To avoid further problems with the user locale, also explicit
UTF-8 encoding for the generated C files.

Explicit both input/output are plain text by using the 't' mode.

This fixes:

  $ /usr/bin/python3 scripts/decodetree.py test.decode
  Traceback (most recent call last):
    File "scripts/decodetree.py", line 1397, in <module>
      main()
    File "scripts/decodetree.py", line 1308, in main
      parse_file(f, toppat)
    File "scripts/decodetree.py", line 994, in parse_file
      for line in f:
    File "/usr/lib/python3.6/encodings/ascii.py", line 26, in decode
      return codecs.ascii_decode(input, self.errors)[0]
  UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 80:
  ordinal not in range(128)

Reported-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
v2: utf-8 output too (Peter)
    explicit default text mode.
---
 scripts/decodetree.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/scripts/decodetree.py b/scripts/decodetree.py
index 47aa9caf6d1..d3857066cfc 100644
--- a/scripts/decodetree.py
+++ b/scripts/decodetree.py
@@ -1304,7 +1304,7 @@ def main():
 
     for filename in args:
         input_file = filename
-        f = open(filename, 'r')
+        f = open(filename, 'rt', encoding='utf-8')
         parse_file(f, toppat)
         f.close()
 
@@ -1324,7 +1324,7 @@ def main():
         prop_size(stree)
 
     if output_file:
-        output_fd = open(output_file, 'w')
+        output_fd = open(output_file, 'wt', encoding='utf-8')
     else:
         output_fd = sys.stdout
 
-- 
2.26.2