rpi_network_conn.py updates

[delirious-lettuce]

• Reorder imports as suggested by PEP8

get_wifi_list

• Remove assignment to wlan_status since it wasn't being used for anything
• Remove returncode since it wasn't being used for anything
• Return [] if sudo ifup wlan0 fails. It would seem if the wifi is down, the next call to check nearby wifi access points will likely fail as well.
• Remove redundant parentheses
• Return [] if sudo iwlist wlan0 scan fails. It doesn't seem to make sense to try to iterate an empty list, create a set out of an empty list and then try to sort an empty set.
• range loop replaced with enumerate since both the index and value are needed
• On the worst case, iw_list[x].strip() was being created 5 times. Also, each instance was then creating another slice. To cut down on unnecessary copies, the current variable saves the stripped current line.
• Using str.startswith doesn't create unnecessary copies either
• end variable was created to reuse the same slice 4 times
• Remove list(...) inside of sorted(...) since it was creating an unnecessary list instead of just creating the sorted list directly from set(wifi_list)

add_wifi

• Create ssid once instead of creating it via concatenation on each iteration of the loop
• Create wifi_key_info once instead of (potentially) multiple times inside the loop (also, if wifi_exists is False)
• Use xrange instead of range
• Remove redundant parentheses
• Simplify network string creation using a multi-line string and textwrap.dedent to keep proper indentation
• Use file.writelines instead of file.write for each separate line

internet_status

• Remove assignment to response since it wasn't being used for anything
• return False immediately if urllib2.URLError is raised
• Move return True to the else statement (for readability and to stay consistent with other project files)

reset_wifi

• Use a multi-line string and textwrap.dedent to create lines
• Remove assignment to vpn_status since it wasn't being used for anything
• Remove returncode since it wasn't being used for anything
• return False immediately if CalledProcessError is raised
• return True in the else since CalledProcessError is only raised for a non-zero exit code (no need to check returncode == 0)