fix winreg bug in pcan (#802)

only import winreg when on Windows

Author: tamenol

can/interfaces/pcan/basic.py

@@ -14,7 +14,9 @@
 from string import *
 import platform
 import logging
-import winreg
+
+if platform.system() == "Windows":
+    import winreg
 
 
 logger = logging.getLogger("can.pcan")