py3: make tests/svn-safe-append.py compatible with python 3

Differential Revision: https://phab.mercurial-scm.org/D4671

tests/svn-safe-append.py

@@ -9,6 +9,10 b' import os'
 import stat
 import sys
 
+if sys.version_info[0] >= 3:
+    text = os.fsencode(sys.argv[1])
+    fname = os.fsencode(sys.argv[2])
+else:
 text = sys.argv[1]
 fname = sys.argv[2]
 
@@ -16,7 +20,7 b' f = open(fname, "ab")'
 try:
     before = os.fstat(f.fileno())[stat.ST_MTIME]
     f.write(text)
-    f.write("\n")
+    f.write(b"\n")
 finally:
     f.close()
 inc = 1