https://github.com/jliljebl/flowblade/pull/1233

Make python-libusb1 optional for Flowblade releases using Flowblade/usbhid.py.

--- a/Flowblade/usbhid.py
+++ b/Flowblade/usbhid.py
@@ -28,7 +28,12 @@ input from the device and triggering action happens in the individual USB HID
 
 from gi.repository import GObject
 
-import usb1
+try:
+    import usb1
+except ImportError as e:
+    # USB jog/shuttle support is optional, so keep application startup working.
+    usb1 = None
+    _usb1_import_error = e
 
 import time
 
@@ -78,6 +83,10 @@ def start_usb_hid_input(device_config_name):
     global usb_driver_ctx
     global usb_hid_input_id
 
+    if usb1 is None:
+        raise UsbHidError("USB HID support requires python-libusb1: %s" % \
+                          (str(_usb1_import_error),))
+
     if usb_driver_ctx is not None:
         raise UsbHidError("USB HID device already in use")