Error message

• Warning: unlink(/home/defense/domains/360defense.nl/public_html/sites/www.warriorhub.com/files/xmlsitemap/NXhscRe0440PFpI5dSznEVgmauL25KojD7u4e9aZwOM/1.xml) [function.unlink]: Permission denied in drupal_unlink() (line 2151 of /home/defense/domains/360defense.nl/public_html/includes/file.inc).
• Warning: XMLWriter::openUri(/home/defense/domains/360defense.nl/public_html/sites/www.warriorhub.com/files/xmlsitemap/NXhscRe0440PFpI5dSznEVgmauL25KojD7u4e9aZwOM/1.xml) [xmlwriter.openuri]: failed to open stream: Permission denied in XMLSitemapWriter->openUri() (line 40 of /home/defense/domains/360defense.nl/public_html/sites/all/modules/xmlsitemap/xmlsitemap.xmlsitemap.inc).
• Warning: XMLWriter::openUri() [xmlwriter.openuri]: xmlNewTextWriterFilename : cannot open uri in XMLSitemapWriter->openUri() (line 40 of /home/defense/domains/360defense.nl/public_html/sites/all/modules/xmlsitemap/xmlsitemap.xmlsitemap.inc).
• Warning: Cannot modify header information - headers already sent by (output started at /home/defense/domains/360defense.nl/public_html/includes/common.inc:2567) in drupal_send_headers() (line 1018 of /home/defense/domains/360defense.nl/public_html/includes/bootstrap.inc).
• XMLSitemapGenerationException: Could not open file public://xmlsitemap/NXhscRe0440PFpI5dSznEVgmauL25KojD7u4e9aZwOM/1.xml for writing. in XMLSitemapWriter->openUri() (line 42 of /home/defense/domains/360defense.nl/public_html/sites/all/modules/xmlsitemap/xmlsitemap.xmlsitemap.inc).