Use unicode in os.path.abspath (https://bugs.python.org/issue17320)

Author: g1itch

src/bitmessagemain.py

@@ -12,7 +12,7 @@
 import os
 import sys
 
-app_dir = os.path.dirname(os.path.abspath(__file__))
+app_dir = os.path.dirname(os.path.abspath(unicode(__file__)))
 os.chdir(app_dir)
 sys.path.insert(0, app_dir)