python: improve python trace user experience

[yihong0618]

Add a simple way to support trace python file without shebang and be an executable file.

Fixed: #1890

with this path we can trace python file just like

g.py like

import sys
import urllib.request

def open_file(name):
    try:
        return open(name)
    except:
        return urllib.request.urlopen(name)

def count_word(file_obj, word):
    n = 0
    content = str(file_obj.read())
    for ln in content.split('\n'):
        n += ln.count(word)
    return n

if __name__ == '__main__':
    url = 'https://github.com/namhyung/uftrace'
    word = 'uftrace'
    if len(sys.argv) > 1:
        url = sys.argv[1]
    if len(sys.argv) > 2:
        word = sys.argv[2]

    f = open_file(url)
    n = count_word(f, word)
    print(n)

then

uftrace g.py

[yskelg]

Hi, @yihong0618,

I agree that it's convenient, but we need to consider this feature carefully.
We’ve had similar discussions before. For instance, let's assume there's an access control feature like SE Linuxor App Armor enabled.

If we allow the use of /bin/uftrace but not /bin/python3 in specific user, there's a corner case where uftrace could execute a Python script without a shebang.

Yes, you could still run the script with python g.py, but that would be specific user to allowed to using python executable.