callr 3.7.1

• When copying existing startup files, an additional newline is appended to
  protect against a missing newline at the end of the file. This would
  cause R ignore that line (#205).

• Serialization of objects passed between sessions now uses compress=FALSE
  by default. The default can be changed by setting the
  callr.compress_transport option (#223, @dfalbel).

• We have revamped callr's error objects, with lots of improvements to the
  output.