Use of uninitialized value in sprintf at .../lib/Test2/Formatter/Test2.pm line 397 without a TTY

[ppisar]

I noticed that running the tests started to produce warnings about an undefined value at Test2-Harness-1.000033/lib/Test2/Formatter/Test2.pm:397, if an output is not a terminal:

$ perl -Ilib scripts/yath t/0-load_all.t t/1-pod_name.t t/HashBase.t | cat

** Defaulting to the 'test' command **

( PASSED )  job  1    t/0-load_all.t
( PASSED )  job  2    t/1-pod_name.t
Use of uninitialized value in sprintf at /home/test/fedora/perl-Test2-Harness/Test2-Harness-1.000033/lib/Test2/Formatter/Test2.pm line 397, <__ANONIO__> line 517.
( PASSED )  job  3    t/HashBase.t

                                Yath Result Summary
-----------------------------------------------------------------------------------
     File Count: 3
Assertion Count: 496
      Wall Time: 0.56 seconds
       CPU Time: 0.88 seconds (usr: 0.17s | sys: 0.02s | cusr: 0.59s | csys: 0.10s)
      CPU Usage: 157%
    -->  Result: PASSED  <--

The undefined value is $self->{+COLOR}->{reset} expression.

I could not still narrow down what change triggers it. Also the number of the warnings somehow depends on a number of tests.