work around strange behaviour of _("")

subiquitycore/i18n.py

@@ -29,11 +29,16 @@ syslog.syslog('Final localedir is ' + localedir)
 
 def switch_language(code='en_US'):
     if code != 'en_US' and 'FAKE_TRANSLATE' in os.environ:
-        import builtins
-        builtins.__dict__['_'] = lambda a: '_(%s)' % a
+        def my_gettext(message):
+            return "_(%s)" % message
     elif code:
         translation = gettext.translation('subiquity', localedir=localedir, languages=[code])
-        translation.install()
+        def my_gettext(message):
+            if not message:
+                return message
+            return translation.gettext(message)
+    import builtins
+    builtins.__dict__['_'] = my_gettext
 
 switch_language()