qapi: Open files with encoding='utf-8'

Python 2 happily reads UTF-8 files in text mode, but Python 3 requires
either UTF-8 locale or an explicit encoding passed to open(). Commit
d4e5ec877ca fixed this by setting the en_US.UTF-8 locale. Falls apart
when the locale isn't be available.

Matthias Maier and Arfrever Frehtes Taifersar Arahesis proposed to use
binary mode instead, with manual conversion from bytes to str. Works,
but opening with an explicit encoding is simpler, so do that.

Since Python 2's open() doesn't support the encoding parameter, we
need to suppress it with a version check.

Backports commit de685ae5e9a4b523513033bd6cadc8187a227170 from qemu

qemu/scripts/qapi/common.py

@@ -16,6 +16,7 @@ import errno
 import os
 import re
 import string
+import sys
 try:
     from collections import OrderedDict
 except:
@@ -352,7 +353,10 @@ class QAPISchemaParser(object):
         if incl_abs_fname in previously_included:
             return None
         try:
-            fobj = open(incl_fname, 'r')
+            if sys.version_info[0] >= 3:
+                fobj = open(incl_fname, 'r', encoding='utf-8')
+            else:
+                fobj = open(incl_fname, 'r')
         except IOError as e:
             raise QAPISemError(info, '%s: %s' % (e.strerror, incl_fname))
         return QAPISchemaParser(fobj, previously_included, info)
@@ -1499,7 +1503,11 @@ class QAPISchemaEvent(QAPISchemaEntity):
 class QAPISchema(object):
     def __init__(self, fname):
         self._fname = fname
-        parser = QAPISchemaParser(open(fname, 'r'))
+        if sys.version_info[0] >= 3:
+            f = open(fname, 'r', encoding='utf-8')
+        else:
+            f = open(fname, 'r')
+        parser = QAPISchemaParser(f)
         exprs = check_exprs(parser.exprs)
         self.docs = parser.docs
         self._entity_list = []
@@ -2006,7 +2014,10 @@ class QAPIGen(object):
                 if e.errno != errno.EEXIST:
                     raise
         fd = os.open(pathname, os.O_RDWR | os.O_CREAT, 0o666)
-        f = os.fdopen(fd, 'r+')
+        if sys.version_info[0] >= 3:
+            f = open(fd, 'r+', encoding='utf-8')
+        else:
+            f = os.fdopen(fd, 'r+')
         text = (self._top(fname) + self._preamble + self._body
                 + self._bottom(fname))
         oldtext = f.read(len(text) + 1)