build: python3 support for configure

PR-URL: #30047
Reviewed-By: Christian Clauss <cclauss@me.com>
Reviewed-By: Sam Roberts <vieuxtech@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: David Carlier <devnexen@gmail.com>

configure.py

@@ -11,6 +11,8 @@
 import shlex
 import subprocess
 import shutil
+import io
+
 from distutils.spawn import find_executable as which
 from distutils.version import StrictVersion
 
@@ -1499,10 +1501,11 @@ def write_config(data, name):
   icu_ver_major = None
   matchVerExp = r'^\s*#define\s+U_ICU_VERSION_SHORT\s+"([^"]*)".*'
   match_version = re.compile(matchVerExp)
-  for line in open(uvernum_h).readlines():
-    m = match_version.match(line)
-    if m:
-      icu_ver_major = m.group(1)
+  with io.open(uvernum_h, encoding='utf8') as in_file:
+    for line in in_file:
+      m = match_version.match(line)
+      if m:
+        icu_ver_major = str(m.group(1))
   if not icu_ver_major:
     error('Could not read U_ICU_VERSION_SHORT version from %s' % uvernum_h)
   elif int(icu_ver_major) < icu_versions['minimum_icu']: