add a new translation warning and improve the old one

implements https://github.com/liberapay/salon/issues/520

closes #922

_i18n_warning.html

@@ -1,4 +1,13 @@
+% if state.get('partial_translation')
 <div class="notification notification-warning top">{{ _(
-    "The {language} translation of this page is not yet complete."
+    "The translation of this page from English is not yet complete. {link_start}You can contribute{link_end}."
-    , language=locale
+    , link_start=('<a href="https://hosted.weblate.org/engage/liberapay/{}/?utm_source=liberapay-incomplete-translation-warning">'|safe).format(locale.global_tag)
+    , link_end='</a>'|safe
 ) }}</div>
+% elif state.get('fuzzy_translation')
+<div class="notification notification-warning top">{{ _(
+    "This page contains machine-translated text which hasn't yet been reviewed and might be inaccurate. {link_start}You can contribute{link_end}."
+    , link_start=('<a href="https://hosted.weblate.org/engage/liberapay/{}/?utm_source=liberapay-machine-translation-warning">'|safe).format(locale.global_tag)
+    , link_end='</a>'|safe
+) }}</div>
+% endif

liberapay/i18n/base.py

@@ -124,6 +124,8 @@ class Locale(babel.core.Locale):
             s2 = msg.string
             if isinstance(s2, tuple):
                 s2 = s2[0]
+            if msg.fuzzy:
+                state['fuzzy_translation'] = True
         if not s2:
             s2 = s
             if self.language != 'en':
@@ -148,6 +150,9 @@ class Locale(babel.core.Locale):
                 s2 = msg.string[self.catalog.plural_func(n)]
             except Exception as e:
                 website.tell_sentry(e)
+            else:
+                if msg.fuzzy:
+                    state['fuzzy_translation'] = True
         if not s2:
             s2 = s if n == 1 else p
             if self.language != 'en':

templates/layouts/base.html

@@ -147,7 +147,7 @@
     </div>
 % endif
 
-% if state.get('partial_translation')
+% if state.get('partial_translation') or state.get('fuzzy_translation')
     % include "_i18n_warning.html"
 % endif