vdirsyncer appears to append slash to URL

I have specified a URL that links to a calendar that has a slightly unusual format of https://company.bamboohr.co.uk/feeds/feed.php?id=someauthenticationtoken. I believe that vdirsyncer is appending a / to this URL when making queries, such that the URL becomes https://company.bamboohr.co.uk/feeds/feed.php?id=someauthenticationtoken/ resulting in no valid ICS being found.

I've attached the start of the debug output of the discover command, where it apparently shows the first attempted URL is incorrect.

Environment:

• Your vdirsyncer version 0.16.7
• If applicable, which server software (and which version) you're using: Bamboo HR, which generates a URL that uses a querystring for authentication with a GET parameter token
• Your Python version 3.7.2 (via homebrew)
• Your operating system Mac OS Mojave
• Your config file

$ cat .config/vdirsyncer/config
[general]
status_path = "~/.vdirsyncer/status/"

[pair work_annual_leave]
a = "work_annual_leave_local"
b = "work_annual_leave_remote"
collections = ["from a", "from b"]

[storage work_annual_leave_local]
type = "filesystem"
path = "~/.calendar/work_annual_leave"
fileext = ".ics"

[storage work_annual_leave_remote]
type = "caldav"
read_only = true
url = "https://company.bamboohr.co.uk/feeds/feed.php?id=redacted

• Use vdirsyncer -vdebug for debug output. The output is sensitive, but
  please attach at least the last few lines before the error (if applicable),
  censored as necessary. This is almost always the most useful information.

$ vdirsyncer -vdebug discover
debug: Using 1 maximal workers.
Discovering collections for pair work_annual_leave
work_annual_leave_local:
debug: PROPFIND https://company.bamboohr.co.uk/feeds/feed.php?id=redacted/
...

Thanks for your time.

Start by reproducing the discover command with the BambooHR-style URL from the issue and inspect the URL handling that produces the shown PROPFIND request. Done means the query-string token is preserved without an appended slash and discovery can find the remote ICS resource.