fix: Quieter default non-interactive error handler

* When an error is thrown by `ArgumentParser()$parse_args()` and `interactive()` is `FALSE`
  and `getOption("error")` is `NULL` then
  we now use a quieter default error handler that doesn't output a trailing "Execution halted".

follow-up on #40

DESCRIPTION

@@ -1,7 +1,7 @@
 Package: argparse
 Type: Package
 Title: Command Line Optional and Positional Argument Parser
-Version: 2.1.6
+Version: 2.1.7-0
 Authors@R: c(person("Trevor L", "Davis", role=c("aut", "cre"),
              email="trevor.l.davis@gmail.com",
              comment = c(ORCID = "0000-0001-6341-4639")),

NEWS.md

@@ -1,3 +1,10 @@
+argparse 2.1.7
+==============
+
+* When an error is thrown by `ArgumentParser()$parse_args()` and `interactive()` is `FALSE`
+  and `getOption("error")` is `NULL` then
+  we now use a quieter default error handler that doesn't output a trailing "Execution halted".
+
 argparse 2.1.6
 ==============
 

R/argparse.R

@@ -358,6 +358,10 @@ find_python_cmd <- function(python_cmd = NULL) {
     python_cmd
 }
 
+quieter_error_handler <- function(e) {
+    quit('no', status = 1, runLast = FALSE)
+}
+
 pa_stop <- function(message, r_note) {
     msg <- paste(c(r_note, message), collapse = "\n")
     cnd <- errorCondition(msg,
@@ -368,7 +372,8 @@ pa_stop <- function(message, r_note) {
     } else {
         signalCondition(cnd)
         cat(message, sep = "\n", file = stderr())
-        opt <- options(show.error.messages = FALSE)
+        opt <- options(error = getOption("error",  quieter_error_handler),
+                       show.error.messages = FALSE)
         on.exit(options(opt))
         stop(cnd)
     }