fix python3 syntax

src/python/gp-read-xtandem.py

@@ -3,7 +3,6 @@
 import sys
 sys.path.append("@CMAKE_INSTALL_PREFIX@/lib/groupingprotein")
 
-import codecs
 import xml.sax
 import re
 from xmlstreamwriter import Writer
@@ -103,7 +102,7 @@ command.add_argument('-e', '--evalue', default=0.05, type=float, \
 command.add_argument('-b', '--bug', default=False, type=bool, \
     help='Circumvent X!Tandem bug in refine mode (default: False)')
 command.add_argument('-o', '--outfile', nargs="?", \
-    type=str, default="-", \
+    type=argparse.FileType("w"), default=sys.stdout, \
     help='Save peptide result default:STDOUT')
 command.add_argument('files', metavar='files', nargs='+', \
     help='List of X!Tandem files to process')
@@ -114,12 +113,7 @@ command.add_argument('-v', '--version', action='version', \
 args = command.parse_args()
 
 #Initialise the Output
-if args.outfile == "-":
-    outfile = codecs.getwriter('utf8')(sys.stdout)
-else:
-    outfile = codecs.open(args.outfile, "w", "utf-8")
-    
-writer = Writer(outfile)
+writer = Writer(args.outfile)
 writer.set_auto_formatting(False)
 writer.write_start_document()
 writer.write_start_element("peptide_result")