Make BZ2File.__init__()'s fileobj argument keyword-only.
diff --git a/Doc/library/bz2.rst b/Doc/library/bz2.rst
index dbf938a..7275e12 100644
--- a/Doc/library/bz2.rst
+++ b/Doc/library/bz2.rst
@@ -29,7 +29,7 @@
 (De)compression of files
 ------------------------
 
-.. class:: BZ2File(filename=None, mode='r', buffering=None, compresslevel=9, fileobj=None)
+.. class:: BZ2File(filename=None, mode='r', buffering=None, compresslevel=9, \*, fileobj=None)
 
    Open a bzip2-compressed file.