Fix encoding/decoding in adapter/converter of sqlite for Python3

bytes must be used when storing raw values of adapter in blob
bytes is received by the converter and so it must be decoded into unicode

issue3211

trytond/backend/sqlite/database.py

@@ -419,12 +419,12 @@ class Cursor(CursorInterface):
     def has_constraint(self):
         return False
 
-sqlite.register_converter('NUMERIC', lambda val: Decimal(val))
+sqlite.register_converter('NUMERIC', lambda val: Decimal(val.decode('utf-8')))
 if sys.version_info[0] == 2:
     sqlite.register_adapter(Decimal, lambda val: buffer(str(val)))
     sqlite.register_adapter(bytearray, lambda val: buffer(val))
 else:
-    sqlite.register_adapter(Decimal, lambda val: bytes(str(val)))
+    sqlite.register_adapter(Decimal, lambda val: str(val).encode('utf-8'))
 
 
 def adapt_datetime(val):
@@ -432,7 +432,7 @@ def adapt_datetime(val):
 sqlite.register_adapter(datetime.datetime, adapt_datetime)
 sqlite.register_adapter(datetime.time, lambda val: val.isoformat())
 sqlite.register_converter('TIME', lambda val: datetime.time(*map(int,
-            val.split(':'))))
+            val.decode('utf-8').split(':'))))
 sqlite.register_adapter(datetime.timedelta, lambda val: val.total_seconds())