[MacPorts] #53109: port select fails if invalid exists

[MacPorts]

#53109: port select fails if invalid exists
-------------------------+-----------------
 Reporter:  nhojpatrick  |      Owner:
     Type:  defect       |     Status:  new
 Priority:  Normal       |  Milestone:
Component:  ports        |    Version:
 Keywords:               |       Port:
-------------------------+-----------------
 I've just done a weekly upgrade and a prompt appeared about python. So I
 did as suggested, I then played around with other python versions and
 discovered select doesn't clean up if active versions are uninstalled and
 then you try and install a new version as active.

 $ sudo port select --list python3
 Available versions for python3:
         none (active)
         python35
 $ ls -l /opt/local/etc/select/python3/
 total 32
 -rw-r--r--+ 1 root  admin  145 12 Sep 13:27 base
 lrwxr-xr-x  1 root  admin    8 21 Aug  2015 current -> python34
 -rw-r--r--+ 1 root  admin   20 12 Sep 13:27 none
 -rw-r--r--+ 1 root  admin  154 18 Oct 20:11 python35
 $ sudo port select --set python3 python35
 Selecting 'python35' for 'python3' failed: symlink:
 /opt/local/etc/select/python3/current -> python35: file already exists

 I would attempt a port but no idea where to start and already trying to
 fix the githut portgroup.

 I would guess this could happen with every port select. If an invalid
 symlink exists and you try and set a new one it should delete the existing
 symlink and create it as specified.

--
Ticket URL: <https://trac.macports.org/ticket/53109>
MacPorts <https://www.macports.org/>
Ports system for macOS