[ndnSIM] Error in installing ndnsim 2.7

[Zeinab]

Hello,
I am trying to install ndnsim 2.7 on ubuntu 18.04 . I followed the ndnsim website however I received syntax error after running ./waf command as follows:

Traceback (most recent call last):
  File "<string>", line 3, in <module>
  File "/usr/lib/python2.7/py_compile.py", line 117, in compile
    raise py_exc
py_compile.PyCompileError:   File "/usr/local/lib/python2.7/dist-packages/visualizer/base.py", line 134
    print("Could not load plugin %r: %s" % (filename, str(ex)), file=sys.stderr)
                                                                    ^
SyntaxError: invalid syntax

May I know how I can solve it.
Thanks
Best regards
Zeinab