Update: scapy-python3 is deprecated (2018) and will no longer be updated. scapy>=2.4.0 has merged python 3 compatibility.
The most up-to-date installation method is now
pip3 install scapy>=2.4.0
You may check the installation page in the documentation for other installation methods
Original answer:
Perhaps you are trying to install the package scapy for Python 2, but you need the one for Python 3.
pip install scapy
gave this error:
os.chmod(fname,0755)
^
SyntaxError: invalid token
while
pip3 install scapy-python3
did a proper install.
This error means the octal number is not recognized by Python 3, see PEP 3127:
octal literals must now be specified with a leading “0o” or “0O” instead of “0”;