bimtester: do not break bimtester if translation files are missing, fixes #1910

src/ifcbimtester/bimtester/lang.py

@@ -8,8 +8,21 @@ def _(message):
     return message
 
 
-def switch_locale(locale_dir, locale_id="en"):
+def switch_locale(locale_dir, locale_id):
     global translation
-    newlang = gettext.translation("messages", localedir=locale_dir, languages=[locale_id])
-    newlang.install()
-    translation = newlang.gettext
+    domain = "messages"
+    # https://docs.python.org/3/library/gettext.html
+    mo_file = gettext.find(domain, localedir=locale_dir, languages=[locale_id])
+    if mo_file is not None:
+        print(
+            "Locale will be switched to language '{}'. Translation file found {}"
+            .format(locale_id, mo_file)
+        )
+        newlang = gettext.translation(domain, localedir=locale_dir, languages=[locale_id])
+        newlang.install()
+        translation = newlang.gettext
+    else:
+        print(
+            "Locale can not be switched to '{}'. Translation file (*.mo) not found in {}"
+            .format(locale_id, locale_dir)
+        )