this looks like a real fix

slapos/promise/check_web_page_http_cache_hit/__init__.py

@@ -12,7 +12,7 @@ import re
 
 import pycurl
 
-from email.message import Message
+import email
 from io import BytesIO
 from six.moves.html_parser import HTMLParser
 
@@ -91,7 +91,7 @@ def checkWebpageHttpCacheHit(url_list, resolve_list=[], cookie_jar_path=None):
 
     response_headers.seek(0)
 
-    m = Message(response_headers)
+    m = email.message_from_string(response_headers.get_value())
 
     # see http://labs.omniti.com/people/mark/ats_sa/slides.html#slide-18
     if not any("[cHs" in header for header in m.getheaders('via')) and \