Shouldn't matter, s/he claimed it's in PATH and executable, unless the claim's false. Python doesn't actively modify your PATH in runtime, we don't either, and there's no shell rc in the way since we don't do `shell=True`.
Can't reproduce. Your python just can't launch your `reader`, so your observation about `BROWSER` is expected, as we suppress both stdout and stderr by default for browsers not on the whitelist.
Try these:
```
$ python3 -c 'import subprocess; p = subprocess.Popen(["reader", "https://example.com"]); p.communicate()'
$ python3 -c 'import subprocess; p = subprocess.Popen(["/Users/me/.local/bin/reader", "https://example.com"]); p.communicate()'
$ python3 -c 'import subprocess; subprocess.check_call(["reader", "https://example.com"])'
$ head /Users/me/.local/bin/reader
```