Update git submodules

* Update heat from branch 'master'
  - Merge "Remove six and python 2.7 full support"
  - Remove six and python 2.7 full support
    
    Six is in use to help us to keep support for python 2.7.
    Since the ussuri cycle we decide to remove the python 2.7
    support so we can go ahead and also remove six usage from
    the python code.
    
    Review process and help
    -----------------------
    Removing six introduce a lot of changes and an huge amount of modified files
    To simplify reviews we decided to split changes into several patches to avoid
    painful reviews and avoid mistakes.
    
    To review this patch you can use the six documentation [1] to obtain help and
    understand choices.
    
    Additional informations
    -----------------------
    Changes related to 'six.b(data)' [2]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    
    six.b [2] encode the given datas in latin-1 in python3 so I did the same
    things in this patch.
    
    Latin-1 is equal to iso-8859-1 [3].
    
    This encoding is the default encoding [4] of certain descriptive HTTP
    headers.
    
    I suggest to keep latin-1 for the moment and to move to another encoding
    in a follow-up patch if needed to move to most powerful encoding (utf8).
    
    HTML4 support utf8 charset and utf8 is the default charset for HTML5 [5].
    
    Note that this commit message is autogenerated and not necesserly contains
    changes related to 'six.b'
    
    [1] https://six.readthedocs.io/
    [2] https://six.readthedocs.io/#six.b
    [3] https://docs.python.org/3/library/codecs.html#standard-encodings
    [4] https://www.w3schools.com/charsets/ref_html_8859.asp
    [5] https://www.w3schools.com/html/html_charset.asp
    
    Patch 5 of a serie of 28 patches
    
    Change-Id: Idb037ded55698790fc1658896f1e2dcdce89f3f9

heat

@@ -1 +1 @@
-Subproject commit 5601db2613c5317e94a06752238bc3908b7fb4c4
+Subproject commit 5819dcb0086493dba971b7a8d000f3f6370662ba