Update CHANGES

Author: tony

CHANGES

@@ -9,6 +9,8 @@ current
 - :issue:`303` Add ``common.get_libtmux_version`` which gives the tmux
   version as a loose constraint. Fix linking to terms inside docs, and
   duplicate description of module which sphinx warned about in api.rst.
+- :issue:`266` Fix issue on local tests where env variables would cause
+  show-environment to pause tests indefinitely.
 - *Insert changes/features/fixes for next release here*
 
 libtmux 0.8.4 (2020-10-25)