Fix bug in running hyperopt in windows 10

with preferred encoding in locale differrent from
utf-8

freqtrade/__init__.py

@@ -1,6 +1,11 @@
 """ Freqtrade bot """
 __version__ = 'develop'
 
+import locale
+def getpreferredencoding(do_setlocale=True):
+    return "utf-8"
+locale.getpreferredencoding = getpreferredencoding
+
 if __version__ == 'develop':
 
     try: