Also output interface language in debug messages

src/calibre/debug.py

@@ -181,9 +181,11 @@ def print_basic_debug_info(out=None):
     import platform
     from calibre.constants import (__appname__, get_version, isportable, isosx,
                                    isfrozen, is64bit)
+    from calibre.utils.localization import set_translators
     out(__appname__, get_version(), 'Portable' if isportable else '',
         'embedded-python:', isfrozen, 'is64bit:', is64bit)
     out(platform.platform(), platform.system(), platform.architecture())
+    out('Interface language:', type(u'')(set_translators.lang))
     if iswindows and not is64bit:
         try:
             import win32process

src/calibre/utils/localization.py

@@ -218,6 +218,10 @@ def set_translators():
     if t is None:
         t = NullTranslations()
 
+    try:
+        set_translators.lang = t.info().get('language')
+    except Exception:
+        pass
     t.install(unicode=True, names=('ngettext',))
     # Now that we have installed a translator, we have to retranslate the help
     # for the global prefs object as it was instantiated in get_lang(), before
@@ -226,6 +230,9 @@ def set_translators():
     prefs.retranslate_help()
 
 
+set_translators.lang = None
+
+
 _iso639 = None
 _extra_lang_codes = {
         'pt_BR' : _('Brazilian Portuguese'),