utils: add utility functions for managing current language

utils.py

@@ -0,0 +1,29 @@
+from contextlib import contextmanager
+
+from quixote import get_request
+
+@contextmanager
+def current_language(language):
+    global __current_language
+    old_current_language = __current_language
+    try:
+        yield
+    finally:
+        __current_language = old_current_language
+
+def for_user(identity):
+    return current_language(identity.get_preferred_language())
+
+__current_language = None
+
+def get_for_current_language(dictionary, key, default=None):
+    request = get_request()
+    language = __current_language
+    if language is None:
+        language = request.language
+    if not language is None:
+        locale_key = '{0}-{1}'.format(key, language)
+        if locale_key in dictionary:
+            return dictionary[locale_key]
+    return dictionary.get(key, default)
+