Fix "Error with time data"

Automatically and silently default to "None" when an invalid date is encountered.
Resolves some-programs#70

exitwp.py

@@ -176,6 +176,11 @@ def gi(q, unicode_wrap=True, empty=False):
         'items': parse_items(),
     }
 
+def format_date(date_text,date_format):
+    try:
+        datetime.strptime(date_text, date_format)
+    except ValueError:
+        'None'
 
 def write_jekyll(data, target_format):
 
@@ -292,8 +297,7 @@ def get_attachment_path(src, dir, dir_prefix='images'):
             'title': i['title'],
             'link': i['link'],
             'author': i['author'],
-            'date': datetime.strptime(
-                i['date'], '%Y-%m-%d %H:%M:%S').replace(tzinfo=UTC()),
+            'date': format_date(i['date'], '%Y-%m-%d %H:%M:%S'),
             'slug': i['slug'],
             'wordpress_id': int(i['wp_id']),
             'comments': i['comments'],