When invoking repo list, do *not* collect stderr.

Stderr may include a message stating "you should upgrade your repo script",
breaking this code's assumptions.

BUG=None
TEST=Manual validation

Change-Id: I44f9f1316debf7fb1954c595f80f4d121c2263a1
Reviewed-on: https://gerrit.chromium.org/gerrit/24581
Reviewed-by: Brian Harring <ferringb@chromium.org>
Tested-by: Brian Harring <ferringb@chromium.org>
1 file changed