Error on file-write errors

generate.php

@@ -108,6 +108,8 @@ private function saveManifests(array $data): void {
             throw new \RuntimeException(sprintf('Directory "%s" was not created', $folder));
         }
 
+        is_writable()
+
         $replacements = [
             '%version%' => $this->version,
             '%releasedate%' => $data['date'],
@@ -119,11 +121,15 @@ private function saveManifests(array $data): void {
             '%versionmin%' => str_replace('.', '', $this->version),
         ];
 
-        foreach ($files as $file) {
-            $targetFile = self::BASE_PATH . '/' . $this->version . '/' . str_replace('(version)', $this->version, $file);
-            $file = file_get_contents(self::BASE_PATH . '/templates/' . $file);
-            $file = strtr($file, $replacements);
-            file_put_contents($targetFile, $file);
+        foreach ($files as $fileName) {
+            $targetFile = self::BASE_PATH . '/' . $this->version . '/' . str_replace('(version)', $this->version, $fileName);
+            $fileContents = file_get_contents(self::BASE_PATH . '/templates/' . $fileName);
+            $fileContents = strtr($fileContents, $replacements);
+            file_put_contents($targetFile, $fileContents);
+
+            if (!file_exists($targetFile)) {
+                throw new \RuntimeException('Unable to write to file: '. $targetFile);
+            }
         }
     }