Hello,
I have a check_mk instance (2.0) deployed in Docker. In there, I have a custom notification sripts that’s supposed to open SNOW tickets. Unfortunately it fails with below error:

2021-07-28 10:29:57,777 [20] [cmk.base.notify]      Output: Traceback (most recent call last):
2021-07-28 10:29:57,777 [20] [cmk.base.notify]      Output:   File "/omd/sites/cmk/local/share/check_mk/notifications/sr_servicenow_plugin", line 293, in <module>
2021-07-28 10:29:57,778 [20] [cmk.base.notify]      Output:     Plugin().notify()
2021-07-28 10:29:57,778 [20] [cmk.base.notify]      Output:   File "/omd/sites/cmk/local/share/check_mk/notifications/sr_servicenow_plugin", line 290, in notify
2021-07-28 10:29:57,778 [20] [cmk.base.notify]      Output:     self.adapter.notify()
2021-07-28 10:29:57,778 [20] [cmk.base.notify]      Output:   File "/omd/sites/cmk/local/share/check_mk/notifications/sr_servicenow_plugin", line 186, in notify
2021-07-28 10:29:57,778 [20] [cmk.base.notify]      Output:     import requests
2021-07-28 10:29:57,778 [20] [cmk.base.notify]      Output: ImportError: No module named requests
I had installed pip to install the requests module but according to it, it was already installed. I changed the header of the script to #!/usr/bin/python3 and then when I forced notification logs showed something different:
2021-07-27 15:37:11,696 [20] [cmk.base.notify]   * notifying cmkadmin via sr_servicenow_plugin, parameters: --debug, bulk: no
2021-07-27 15:37:11,696 [20] [cmk.base.notify]      executing /omd/sites/cmk/local/share/check_mk/notifications/sr_servicenow_plugin
2021-07-27 15:37:11,703 [40] [cmk.base.notify]     ERROR:
Traceback (most recent call last):
  File "/omd/sites/cmk/lib/python3/cmk/base/notify.py", line 633, in _process_notifications
    call_notification_script(plugin_name, context)
  File "/omd/sites/cmk/lib/python3/cmk/base/notify.py", line 1490, in call_notification_script
    p = subprocess.Popen([path],
  File "/omd/sites/cmk/lib/python3.8/subprocess.py", line 854, in __init__
    self._execute_child(args, executable, preexec_fn, close_fds,
  File "/omd/sites/cmk/lib/python3.8/subprocess.py", line 1702, in _execute_child
    raise child_exception_type(errno_num, err_msg, err_filename)
FileNotFoundError: [Errno 2] No such file or directory: '/omd/sites/cmk/local/share/check_mk/notifications/sr_servicenow_plugin'
But the mentioned file is under the path of the error? Under the OMD I see 3 folders with python:
OMD[cmk]:~/lib$ ls -l |grep pyth
lrwxrwxrwx   1 root root      11 May 26 07:06 check_mk -> python3/cmk/
lrwxrwxrwx   1 root root      19 May 26 07:06 libpython3.8.so -> libpython3.8.so.1.0
-rw-r--r--   1 root root 3424224 May 26 07:06 libpython3.8.so.1.0
-rw-r--r--   1 root root   14112 May 26 07:06 libpython3.so
drwxr-xr-x   2 root root    4096 May 26 07:06 python/
drwxr-xr-x 192 root root   12288 May 26 15:48 python3/
drwxr-xr-x  34 root root    4096 May 26 15:48 python3.8/
OMD[cmk]:~/lib$ pwd
/omd/sites/cmk/lib
python3.8 contains the requests module. How should I proceed with this?
              
This is what I did. Result was the second error I pasted above:
FileNotFoundError: [Errno 2] No such file or directory: '/omd/sites/cmk/local/share/check_mk/notifications/sr_servicenow_plugin'
While the file is there. One thing though - when I did a “ls -l” on that path the file had an * after its name. I don’t know what that means.
-rwxrwxr-x 1 cmk cmk 10747 Jul 27 15:39 sr_servicenow_plugin*
-rwxrwxr-x 1 cmk cmk 10502 Jun 23 09:58 sr_servicenow_plugin_high*
 hyperqbe:
when I did a “ls -l” on that path the file had an * after its name. I don’t know what that means.
This is because ls is aliased to ls -F and will output markers for filetypes. The * denotes executable files.
              
Syntax seems to be ok, now I have different error
2021-07-29 13:27:19,442 [20] [cmk.base.notify]      Output: Traceback (most recent call last):
2021-07-29 13:27:19,442 [20] [cmk.base.notify]      Output:   File "/omd/sites/cmk/local/share/check_mk/notifications/sr_servicenow_plugin", line 292, in <module>
2021-07-29 13:27:19,442 [20] [cmk.base.notify]      Output:     Plugin().notify()
2021-07-29 13:27:19,442 [20] [cmk.base.notify]      Output:   File "/omd/sites/cmk/local/share/check_mk/notifications/sr_servicenow_plugin", line 288, in notify
2021-07-29 13:27:19,443 [20] [cmk.base.notify]      Output:     self.__parse__()
2021-07-29 13:27:19,443 [20] [cmk.base.notify]      Output:   File "/omd/sites/cmk/local/share/check_mk/notifications/sr_servicenow_plugin", line 279, in __parse__
2021-07-29 13:27:19,443 [20] [cmk.base.notify]      Output:     self.data = self.__parse_rulebased__() # data is dict
2021-07-29 13:27:19,443 [20] [cmk.base.notify]      Output:   File "/omd/sites/cmk/local/share/check_mk/notifications/sr_servicenow_plugin", line 247, in __parse_rulebased__
2021-07-29 13:27:19,443 [20] [cmk.base.notify]      Output:     context = dict([
2021-07-29 13:27:19,443 [20] [cmk.base.notify]      Output:   File "/omd/sites/cmk/local/share/check_mk/notifications/sr_servicenow_plugin", line 248, in <listcomp>
2021-07-29 13:27:19,443 [20] [cmk.base.notify]      Output:     (var[7:], value.decode('utf-8'))
2021-07-29 13:27:19,443 [20] [cmk.base.notify]      Output: AttributeError: 'str' object has no attribute 'decode'
It’s for this part of code:
        self.logger.debug("Parsing rulebased data from env variables")
        context = dict([
            (var[7:], value.decode('utf-8'))
            for (var, value) in os.environ.items()
            if var.startswith("NOTIFY_")])
I’m not sure if I can share the full script.
              
Thank you all for assistance. I was able to get the script working. What had to be done is what @r.sander mentioned. Change
#!/usr/bin/python
#!/usr/bin/env python3
Then update
(var[7:], value.decode('utf-8'))
(var[7:], value)
as decode is not necessary in py3.