Log Message:
Update ruby-minitest to 5.10.2.

=== 5.10.2 / 2017-05-09

* 1 minor enhancement:

  * Added suggestion in minitest/hell to install minitest/proveit.

* 7 bug fixes:

  * Expand MT6 to Minitest 6. (xaviershay)
  * Fixed location of assert_send deprecation. (rab)
  * Fixed location of nil assert_equal deprecation to work with expectations. \ 
(jeremyevans)
  * Fixed minitest/hell to use parallelize_me! (azul)
  * Made deprecation use warn so -W0 will silence it.
  * Workaround for rdoc nodoc generation bug that totally f'd up minitest doco. \ 
(Paxa)
  * Write aggregated_results directly to the IO object to avoid mixed encoding \ 
errors. (tenderlove)