simplify

Author: staabm

src/Rules/Regexp/RegularExpressionPatternRule.php

@@ -128,12 +128,12 @@ private function validatePattern(string $pattern): ?string
 			Strings::match('', $pattern);
 		} catch (RegexpException $e) {
 			if (str_contains($e->getMessage(), 'UTF-8 error')) {
-				$lastColonPos = strrpos($e->getMessage(), ':');
-				if ($lastColonPos === false) {
+				$patternPos = strpos($e->getMessage(), 'pattern:');
+				if ($patternPos === false) {
 					throw new ShouldNotHappenException();
 				}
 				// strip invalid utf-8 pattern contents to keep the error message NEON parsable.
-				return substr($e->getMessage(), 0, $lastColonPos);
+				return substr($e->getMessage(), 0, $patternPos);
 			}
 			return $e->getMessage();
 		}