Add @staticmethod to __currency

bot/coins.py

@@ -11,13 +11,14 @@ from . import Plugin
 class Coins(Plugin):
     API_URL = 'https://api.cryptowat.ch/markets/{market}/{crypto}{currency}/summary'
 
+    @staticmethod
     def __currency(name, prefix=None, suffix=None):
-	def str(value):
+	def tostr(value):
 	    return '{prefix}{value:,.2f}{suffix}'.format(
 		    prefix=prefix or '',
 		    suffix=suffix or ('' if (prefix or suffix) else (' ' + name)),
 		    value=value)
-	return str
+	return tostr
 
     CURRENCIES = {
         'usd': __currency('usd', prefix='$'),