Fix PEP8 errors in performance-test.py

Author: chrisb2

performance-test.py

@@ -12,17 +12,21 @@
 
 ina = INA219(SHUNT_OHMS, MAX_EXPECTED_AMPS, log_level=logging.INFO)
 
+
 def init():
     ina.configure(ina.RANGE_16V, ina.GAIN_AUTO)
 
+
 def read():
     for x in range(0, READS):
-        v = ina.voltage()
+        ina.voltage()
+
 
 if __name__ == "__main__":
     init()
     start = time.time()
     read()
     finish = time.time()
     elapsed = (finish - start) * 1000000
-    print("Read time (average over %d reads): %d microseconds" % (READS, int(elapsed / READS)))
+    print("Read time (average over %d reads): %d microseconds" %
+          (READS, int(elapsed / READS)))