Safely interpolate in environment variable reporting

The msg parameter to status is a format string. If we pass a string
directly to it, then we have to be careful to escape any formatting
characters.

However, we can just do the interpolation directly in the status call
instead, which is less code.

1 files changed, 2 insertions, 2 deletions

diff --git a/morphlib/util.py b/morphlib/util.py
index ae1df56a..dc3dd474 100644
--- a/morphlib/util.py
+++ b/morphlib/util.py
@@ -228,8 +228,8 @@ def log_environment_changes(app, current_env, previous_env): # pragma: no cover
             value_msg = '(value hidden)'
         else:
             value_msg = '= "%s"' % value
-        msg = '%s environment variable %s %s' % (event, key, value_msg)
-        app.status(msg=msg, chatty=True)
+        app.status(msg='%(event)s environment variable %(key)s %(value)s',
+                   event=event, key=key, value=value_msg, chatty=True)
 
     for key in current_env.keys():
         if key not in previous_env: