Increase the usage of augmented assignment statements

[elfring]

:eyes: Some source code analysis tools can help to find opportunities for improving software components. :thought_balloon: I propose to increase the usage of augmented assignment statements accordingly.

diff --git a/can/interfaces/gs_usb.py b/can/interfaces/gs_usb.py
index 447cdf4..3c619d6 100644
--- a/can/interfaces/gs_usb.py
+++ b/can/interfaces/gs_usb.py
@@ -44,13 +44,13 @@ class GsUsbBus(can.BusABC):
         can_id = msg.arbitration_id
 
         if msg.is_extended_id:
-            can_id = can_id | CAN_EFF_FLAG
+            can_id |= CAN_EFF_FLAG
 
         if msg.is_remote_frame:
-            can_id = can_id | CAN_RTR_FLAG
+            can_id |= CAN_RTR_FLAG
 
         if msg.is_error_frame:
-            can_id = can_id | CAN_ERR_FLAG
+            can_id |= CAN_ERR_FLAG
 
         # Pad message data
         msg.data.extend([0x00] * (CAN_MAX_DLC - len(msg.data)))
diff --git a/can/interfaces/usb2can/serial_selector.py b/can/interfaces/usb2can/serial_selector.py
index fcc9512..a4e96b9 100644
--- a/can/interfaces/usb2can/serial_selector.py
+++ b/can/interfaces/usb2can/serial_selector.py
@@ -18,9 +18,9 @@ def WMIDateStringToDate(dtmDate) -> str:
         strDateTime = dtmDate[4] + dtmDate[5] + "/"
 
     if dtmDate[6] == 0:
-        strDateTime = strDateTime + dtmDate[7] + "/"
+        strDateTime += dtmDate[7] + "/"
     else:
-        strDateTime = strDateTime + dtmDate[6] + dtmDate[7] + "/"
+        strDateTime += dtmDate[6] + dtmDate[7] + "/"
         strDateTime = (
             strDateTime
             + dtmDate[0]