Use with keyword for opening target file

Simply reading a file is dangerous, it might happens that the file
might be open but not closed will leads to ResourceWarning: unclosed
file error, It is necessary to use with keyword which will close the
file first and then allow it to open it.

Changing r mode to rb mode as in Python3, While r mode is used then
it reads the file based on file encoding provided but with rb mode
it reads the stream as a binary which avoides the encoding issue.

Change-Id: Ia48c1cb0e436ac2c53fc6bd46c4a906c70a51325

tripleoclient/v1/tripleo_deploy.py

@@ -1089,7 +1089,8 @@ class Deploy(command.Command):
             raise exceptions.DeploymentError(msg)
 
         target = override_file
-        data = open(target, 'r').read()
+        with open(target, 'rb') as fb:
+            data = fb.read()
         if not data.strip():
             # since an empty file isn't valid yaml, let's be more specific
             msg = (_("hieradata override file (%s) cannot be empty") % target)