If you get this error:

Traceback (most recent call last):
  File "/usr/local/bin/scapy", line 10647, in ?
    class Conf(ConfClass):
  File "/usr/local/bin/scapy", line 10670, in Conf
    iface = get_working_if()
  File "/usr/local/bin/scapy", line 2067, in get_working_if
    except pcap.pcapc.EXCEPTION:
AttributeError: 'module' object has no attribute 'pcapc'

This is becuase you aren't running scapy as root. Run it as root.

If you still get this error message, it's likely due to pcap failing to find usable network interfaces. This means you have no interfaces in the UP state. It doesn't count lo0 as a real interface, I guess?