Add issue numbers

Author: slozier

Src/IronPythonTest/Cases/CPythonCasesManifest.ini

@@ -889,6 +889,7 @@ Ignore=true
 
 [CPython.test_stringprep]
 Ignore=true
+Reason=Requires unicode 3.2.0 data - https://github.com/IronLanguages/ironpython3/issues/691
 
 [CPython.test_strptime]
 Ignore=true
@@ -1024,6 +1025,7 @@ Ignore=true
 
 [CPython.test_ucn]
 Ignore=true
+Reason=Blocked by https://github.com/IronLanguages/ironpython3/issues/691
 
 [CPython.test_unicode] # IronPython.test_unicode_stdlib
 Ignore=true