From a "best practices" perspective you should store your python somewhere not privileged, C:\Program Files is probably the worst place. Also personally I hate paths with spaces in them, they always cause problems for me eventually somewhere. (So, Microsoft blew it when they named it "Program Files"! 🙂
Anyway -- just don't do that, put them someplace like for example C:\Users\YOURACCOUNT\scripts
I usually keep them with the project I am working on so I can find them later. C:\Users\MYACCOUNT\Documents\MYPROJECTNAME\scripts\
Since your command line prompt says (load_csv) on it I assume you got conda going and activated it added the modules. That means in that command window that python works from anywhere, you don't need to be in the folder C:\Program Files\ArcGIS\Server\framework\runtime\ArcGIS\bin\Python\Scripts and that is probably the wrong place anyway.
If you do "conda info" it will tell you everything it knows about the active set up, the first two lines will show the environment which is probably "load_csv" for you and then the location, for me right now it's
$ conda info
active environment : arcgispro29
active env location : C:\Users\bwilson\.conda\envs\arcgispro29
.
.
.
If I run python while the conda environment is activated, then it will point at the one in "C:\Users\bwilson\.conda\envs\arcgispro29"
It's probably running the right python in your test (the one in the load_csv environment). To get it to run the wrong one (the one in Program Files) you would need to put a dot in front like ".\python" to say "use the python right here in this folder not the one on my PATH".
I think the problem now is you are not logging in and you are asking for access to a restricted service in GIS, try adding username and password, for example "gis = GIS(url,user,pass)"
The error code you see (403) is a HTTP "access forbidden" error so it's running the script and hitting the web server and the URL is correct but there are permissions issues.
You could wrap the GIS call in a try / except block to get a friendlier message,
url="https:///////etc/etc/etc"
user="joe"
pass="secret"
try:
gis = gis(url,user,pass)
except Exception as e:
print("Login failed,",e)
exit(-1)