Possible fix/workaround for OSX frequency trimming

debian/changelog

@@ -1,3 +1,9 @@
+stcgal (1.3) unstable; urgency=low
+
+  * Update to 1.3
+
+ -- Grigori Goronzy <greg@chown.ath.cx>  Sat, 10 Jun 2017 10:01:07 +0200
+
 stcgal (1.2) unstable; urgency=low
 
   * Update to 1.2

stcgal/protocols.py

@@ -114,7 +114,11 @@ class StcBaseProtocol:
 
         # read and check frame start magic
         packet = bytes()
-        packet += self.read_bytes_safe(1)
+        # XXX: skip extraneous 0xFE byte?
+        leading = self.read_bytes_safe(1)
+        if leading == 0xfe:
+            leading = self.read_bytes_safe(1)
+        packet += leading
         # Some (?) BSL versions don't send a frame start with the status
         # packet. Let's be liberal and accept that always, just in case.
         if packet[0] == self.PACKET_MCU[0]: