fix(brew_unknown_command): make subprocess.check_output return str
diff --git a/thefuck/rules/brew_unknown_command.py b/thefuck/rules/brew_unknown_command.py
index 6664d8e88..26c0924f8 100644
--- a/thefuck/rules/brew_unknown_command.py
+++ b/thefuck/rules/brew_unknown_command.py
@@ -12,7 +12,8 @@
 def _get_brew_path_prefix():
     """To get brew path"""
     try:
-        return subprocess.check_output(['brew', '--prefix']).strip()
+        return subprocess.check_output(['brew', '--prefix'],
+                                       universal_newlines=True).strip()
     except:
         return None
 

Fix `TypeError: can't concat bytes to str` error on Python 3.4.
