check for write permission on fasta files : this is odd, nut required by X\!Tandem

src/core/tandem_run/tandembatchprocess.cpp

@@ -89,6 +89,13 @@ TandemBatchProcess::writeXmlDatabaseFile(QXmlStreamWriter *p_out)
   // coli 27J42_WGS_ECOLI_1.fasta"></file>
   for(QString fasta_file : _tandem_run_batch._fasta_file_list)
     {
+
+      if(!QFileInfo(fasta_file).isWritable())
+        {
+          throw pappso::PappsoException(
+            QObject::tr("error : Fasta file %1 is not writable.\n\"tandem.exe\" requires write permission on fasta files to run correctly.")
+              .arg(_tmp_database_file.fileName()));
+        }
       p_out->writeStartElement("file");
       p_out->writeAttribute("format", "peptide");
       p_out->writeAttribute("URL", fasta_file);