v3.4.0

• Processx has now better error messages, in particular, all errors from C
  code contain the file name and line number, and the system error code
  and message (where applicable).

• Processx now sets the .Last.error variable for every un-caught processx
  error to the error condition, and also sets .Last.error.trace to its
  stack trace.

• run() now prints the last 10 lines of the standard error stream on
  error, if echo = FALSE, and it also prints the exit status of the
  process.

• run() now includes the standard error in the condition signalled on
  interrupt.

• process now supports creating pseudo terminals on Unix systems.

• conn_create_pipepair() gets new argument to set the pipes as blocking
  or non-blocking.

• process does not set the inherited extra connections as blocking,
  and it also does not close them after starting the subprocess.
  This is now the responsibility of the user. Note that this is a
  breaking change.

• run() now passes extra ... arguments to process$new().

• run() now does not error if the process is killed in a callback.