Close manifest file.
This change doesn't make any difference to CPython, but is a necessary fix for Jython.
diff --git a/Lib/distutils/command/sdist.py b/Lib/distutils/command/sdist.py
index 3dfe6f2..a06b195 100644
--- a/Lib/distutils/command/sdist.py
+++ b/Lib/distutils/command/sdist.py
@@ -383,6 +383,7 @@
             if line[-1] == '\n':
                 line = line[0:-1]
             self.filelist.append(line)
+        manifest.close()
 
     # read_manifest ()