+9th July 2020
+-------------
+
+IF YOU ARE ON THE MASTER BRANCH, STOP (I REPEAT) STOP READING THIS
+DOCUMENT AND READ UPGRADE.mojo FIRST.
+
+
+If you are not on an existing 'mojo' branch, or you have a build less
+than 260, please stop reading as well and read UPGRADE.mojo (in the
+section about installing packages), as you need to install some extra
+packages before restarting the new version of the code. If in doubt
+try installing the packages again as this will either confirm that all
+is already done or will install what's missing.
+
+Assuming you have done the above: