constraints: update test to match old and new constraint error messages

The compiler now uses the phrase "does not satisfy" when a constraint
is not satisfied by a type parameter (before 1.20 it used the phrase
"does not implement").

Fixes golang/go#57615.

Change-Id: Ibc8461b2f293393f4f7cac7d330bb863b3a15c28
Reviewed-on: https://go-review.googlesource.com/c/exp/+/460460
Reviewed-by: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
diff --git a/constraints/constraints_test.go b/constraints/constraints_test.go
index 5bc43a9..28af970 100644
--- a/constraints/constraints_test.go
+++ b/constraints/constraints_test.go
@@ -5,11 +5,11 @@
 package constraints
 
 import (
-	"bytes"
 	"fmt"
 	"os"
 	"os/exec"
 	"path/filepath"
+	"regexp"
 	"runtime"
 	"testing"
 )
@@ -148,9 +148,8 @@
 				t.Error("build succeeded, but expected to fail")
 			} else if len(out) > 0 {
 				t.Logf("%s", out)
-				const want = "does not implement"
-				if !bytes.Contains(out, []byte(want)) {
-					t.Errorf("output does not include %q", want)
+				if !wantRx.Match(out) {
+					t.Errorf("output does not match %q", wantRx)
 				}
 			} else {
 				t.Error("no error output, expected something")
@@ -158,3 +157,5 @@
 		})
 	}
 }
+
+var wantRx = regexp.MustCompile("does not (implement|satisfy)")