Change shebangs to execute python3 explicitly

ddusb.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 """Write an ISO image to a usb drive using dd."""
 
 import argparse

dlaudio.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 """Download audio using youtube-dl, passing
    a specific set of options specified by the user.
 

drivetemp.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 """Check the temperature of a drive.
 Functions:
     verify_device_node(query)