--- a/eric6/MicroPython/CircuitPythonDevices.py	Thu Jul 11 19:48:14 2019 +0200
+++ b/eric6/MicroPython/CircuitPythonDevices.py	Tue Jul 16 20:12:53 2019 +0200
@@ -132,7 +132,7 @@
             oldMode = ctypes.windll.kernel32.SetErrorMode(1)
             try:
                 for disk in 'ABCDEFGHIJKLMNOPQRSTUVWXYZ':
-                    path = '{}:\\'.format(disk)
+                    path = '{0}:\\'.format(disk)
                     if (os.path.exists(path) and
                             getVolumeName(path) == 'CIRCUITPY'):
                         return path