feat: check if environ exists

control/pca9685/pca9685.py

@@ -17,6 +17,9 @@ import math
 import os
 
 
+MOCK_ENV = 'PCA9685_MOCK_SMBUS'
+
+
 class MockSMBus:
     def __init__(self, bus_number):
         self.bus_number = bus_number
@@ -72,7 +75,7 @@ class PWM:
             self.bus_number = 1
         else:
             self.bus_number = bus_number
-        if os.environ['PCA9685_MOCK_SMBUS'] == 'true':
+        if MOCK_ENV in os.environ and os.environ[MOCK_ENV] == 'true':
             self.bus = MockSMBus(self.bus_number)
         else:
             self.bus = SMBus(self.bus_number)