Further fixes for tab-completion TAP tests.

Escape non-printable characters in failure reports, by using Data::Dumper
in Useqq mode.  Also, bump $Test::Builder::Level so the diagnostic
references the calling line, and use diag() instad of note(),
so it shows even in non-verbose mode (per request from Christoph Berg).

Also, give up on trying to test for the specific way that readline
chooses to overwrite existing text in the \DRD -> \drds test.
There are too many variants, it seems, at least on the libedit
side of things.

Dagfinn Ilmari Mannsåker and Tom Lane

Discussion: https://postgr.es/m/20200103110128.GA28967@msg.df7cb.de

Author: tglsfdc

src/bin/psql/t/010_tab_completion.pl

@@ -5,6 +5,7 @@
 use TestLib;
 use Test::More;
 use IPC::Run qw(pump finish timer);
+use Data::Dumper;
 
 if (!defined($ENV{with_readline}) || $ENV{with_readline} ne 'yes')
 {
@@ -52,6 +53,9 @@ sub check_completion
 {
 	my ($send, $pattern, $annotation) = @_;
 
+	# report test failures from caller location
+	local $Test::Builder::Level = $Test::Builder::Level + 1;
+
 	# reset output collector
 	$out = "";
 	# restart per-command timer
@@ -63,7 +67,9 @@ sub check_completion
 	my $okay = ($out =~ m/$pattern/ && !$timer->is_expired);
 	ok($okay, $annotation);
 	# for debugging, log actual output if it didn't match
-	note 'Actual output was "' . $out . "\"\n" if !$okay;
+	local $Data::Dumper::Terse = 1;
+	local $Data::Dumper::Useqq = 1;
+	diag 'Actual output was ' . Dumper($out) . "\n" if !$okay;
 	return;
 }
 
@@ -105,11 +111,9 @@ sub clear_query
 clear_query();
 
 # check case-sensitive keyword replacement
-# XXX the output here might vary across readline versions
-check_completion(
-	"\\DRD\t",
-	"\\DRD\b\b\bdrds ",
-	"complete \\DRD<tab> to \\drds");
+# note: various versions of readline/libedit handle backspacing
+# differently, so just check that the replacement comes out correctly
+check_completion("\\DRD\t", "drds ", "complete \\DRD<tab> to \\drds");
 
 clear_query();