requires.txt is not mandatory for metadata generator

pipdeps/pipdeps.py

@@ -223,7 +223,7 @@ def get_metadata(package, version):
         if item['packagetype'] == 'sdist':
             tmp_file = file_download(item['url'])
             write_metadata(tmp_file)
-            if os.path.isfile('/tmp/requires.txt') and os.path.isfile('/tmp/PKG-INFO'):
+            if os.path.isfile('/tmp/PKG-INFO'):
                 metadata = [
                     line.decode('utf-8') \
                     for line in wheel.metadata.pkginfo_to_metadata('/tmp', '/tmp/PKG-INFO') \