Py3 Fix to import Airfoil DAT files

To prevent error message as per https://forum.freecadweb.org/viewtopic.php?f=3&t=33309#p278902

As it's my first PR, I've tried to follow the advice @triplus gave in https://forum.freecadweb.org/viewtopic.php?f=10&t=30340&start=300#p279079 but please let me know if I'm not providing sufficient information.

src/Mod/Draft/importAirfoilDAT.py

@@ -42,13 +42,16 @@ useDraftWire = True
 def decodeName(name):
 	"decodes encoded strings"
 	try:
-		decodedName = (name.decode("utf8"))
+		decodedName = name
 	except UnicodeDecodeError:
 		try:
 			decodedName = (name.decode("latin1"))
 		except UnicodeDecodeError:
-			print("AirfoilDAT: error: couldn't determine character encoding")
-			decodedName = name
+			try:
+				decodedName = (name.decode("utf8"))
+			except UnicodeDecodeError:
+				print("AirfoilDAT: error: couldn't determine character encoding")
+				decodedName = name
 	return decodedName
 
 def open(filename):