Fix "is not a valid language" on upload

cps/epub.py

@@ -26,6 +26,7 @@ from .helper import split_authors
 from .constants import BookMeta
 
 
+
 def extractCover(zipFile, coverFile, coverpath, tmp_file_name):
     if coverFile is None:
         return None
@@ -83,16 +84,8 @@ def get_epub_info(tmp_file_path, original_file_name, original_file_extension):
         else:
             epub_metadata['description'] = ""
 
-    if epub_metadata['language'] == u'Unknown':
-        epub_metadata['language'] = ""
-    else:
-        lang = epub_metadata['language'].split('-', 1)[0].lower()
-        if len(lang) == 2:
-            epub_metadata['language'] = isoLanguages.get(part1=lang).name
-        elif len(lang) == 3:
-            epub_metadata['language'] = isoLanguages.get(part3=lang).name
-        else:
-            epub_metadata['language'] = ""
+    lang = epub_metadata['language'].split('-', 1)[0].lower()
+    epub_metadata['language'] = isoLanguages.get_lang3(lang)
 
     series = tree.xpath("/pkg:package/pkg:metadata/pkg:meta[@name='calibre:series']/@content", namespaces=ns)
     if len(series) > 0: