New html5lib requires newer version of six.py than that shipped in macOS 10.14.6
https://bugs.webkit.org/show_bug.cgi?id=202830

Autoinstall six along with html5lib.

Patch by Kenneth Russell <kbr@chromium.org> on 2019-10-10
Reviewed by Jonathan Bedard.

* Scripts/webkitpy/thirdparty/__init__.py:
(AutoinstallImportHook._install_mechanize):
(AutoinstallImportHook._install_pytest):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@250998 268f45cc-cd09-0410-ab3c-d52691b4dbfc
diff --git a/Tools/ChangeLog b/Tools/ChangeLog
index a8ba27b..65e89e1 100644
--- a/Tools/ChangeLog
+++ b/Tools/ChangeLog
@@ -1,3 +1,16 @@
+2019-10-10  Kenneth Russell  <kbr@chromium.org>
+
+        New html5lib requires newer version of six.py than that shipped in macOS 10.14.6
+        https://bugs.webkit.org/show_bug.cgi?id=202830
+
+        Autoinstall six along with html5lib.
+
+        Reviewed by Jonathan Bedard.
+
+        * Scripts/webkitpy/thirdparty/__init__.py:
+        (AutoinstallImportHook._install_mechanize):
+        (AutoinstallImportHook._install_pytest):
+
 2019-10-10  Jonathan Bedard  <jbedard@apple.com>
 
         results.webkit.org: Sort out certificates on Catalina
diff --git a/Tools/Scripts/webkitpy/thirdparty/__init__.py b/Tools/Scripts/webkitpy/thirdparty/__init__.py
index 54ad78c..b26e9c0 100644
--- a/Tools/Scripts/webkitpy/thirdparty/__init__.py
+++ b/Tools/Scripts/webkitpy/thirdparty/__init__.py
@@ -125,6 +125,10 @@
         elif '.requests' in fullname:
             self._install_requests()
 
+    def _install_six(self):
+        self._install("https://files.pythonhosted.org/packages/16/d8/bc6316cf98419719bd59c91742194c111b6f2e85abac88e496adefaf7afe/six-1.11.0.tar.gz",
+                              "six-1.11.0/six.py")
+
     def _install_mechanize(self):
         self._ensure_autoinstalled_dir_is_in_sys_path()
         self._install("https://files.pythonhosted.org/packages/0b/02/ae6ceac1baeda530866a85075641cec12989bd8d31af6d5ab4a3e8c92f47/webencodings-0.5.1.tar.gz",
@@ -133,6 +137,7 @@
                              "html5lib-1.0.1/html5lib")
         self._install("https://files.pythonhosted.org/packages/64/f1/1aa4c96dea14e17a955019b0fc4ac1b8dfbc50e3c90970c1fb8882e74a7b/mechanize-0.4.3.tar.gz",
                              "mechanize-0.4.3/mechanize")
+        self._install_six()
 
     def _install_keyring(self):
         self._install("https://files.pythonhosted.org/packages/7d/a9/8c6bf60710781ce13a9987c0debda8adab35eb79c6b5525f7fe5240b7a8a/keyring-7.3.1.tar.gz",
@@ -166,8 +171,7 @@
                               "pluggy-0.6.0/pluggy")
         self._install("https://files.pythonhosted.org/packages/c0/2f/6773347277d76c5ade4414a6c3f785ef27e7f5c4b0870ec7e888e66a8d83/more-itertools-4.2.0.tar.gz",
                               "more-itertools-4.2.0/more_itertools")
-        self._install("https://files.pythonhosted.org/packages/16/d8/bc6316cf98419719bd59c91742194c111b6f2e85abac88e496adefaf7afe/six-1.11.0.tar.gz",
-                              "six-1.11.0/six.py")
+        self._install_six()
         self._install("https://files.pythonhosted.org/packages/a1/e1/2d9bc76838e6e6667fde5814aa25d7feb93d6fa471bf6816daac2596e8b2/atomicwrites-1.1.5.tar.gz",
                               "atomicwrites-1.1.5/atomicwrites")
         self._install("https://files.pythonhosted.org/packages/94/4a/db842e7a0545de1cdb0439bb80e6e42dfe82aaeaadd4072f2263a4fbed23/funcsigs-1.0.2.tar.gz",