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
d4e5ec87 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.
Reported-by: NArfrever Frehtes Taifersar Arahesis <arfrever.fta@gmail.com>
Reported-by: NMatthias Maier <tamiko@43-1.org>
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Message-Id: <20180618175958.29073-2-armbru@redhat.com>
Reviewed-by: NEduardo Habkost <ehabkost@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>

scripts/qapi/common.py

@@ -16,6 +16,7 @@ import errno
 import os
 import re
 import string
+import sys
 from collections import OrderedDict
 
 builtin_types = {
@@ -340,7 +341,10 @@ class QAPISchemaParser(object):
             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)
@@ -1493,7 +1497,11 @@ 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 = []
@@ -2007,7 +2015,10 @@ 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)