macOS Sierra: AppleScript mount volume keeps asking for login
As Apple replied to the ticket referenced in mattdwen's Open Radar link above, as of macOS Sierra 10.12,


  you can no longer create items in /Volumes unless root.


Further, my best understanding of the AppleScript mount volume command is that it doesn't have a way to specify the mount point and consequently it only mounts volumes under /Volumes through the Finder's standard mechanism. So, I don't think you can do it via AppleScript.

But there's another way. You can accomplish the same thing using the lower level mount command:

mkdir -p ~/mnt
mount_smbfs "//my_username:my_password@my_hostname/share" ~/mnt


After mounting the volume this way, you should see a normal "volume" icon appear on your desktop and the ~/mnt directory will appear as "share" when you browse your user directory via Finder.

The one thing missing from this approach is saving the login credentials in Keychain. To do that, you have to do a bit more scripting. Something like this.

Save the password:

security add-generic-password -a my_username -s my_hostname -w my_password


Retrieve the password and mount the share:

pass=$(security find-generic-password -a my_username -s my_hostname -w)
mount_smbfs "//my_username:${pass}@my_hostname/share" ~/mnt


NOTE: If you have special characters in your password, you will probably need to URL encode it, perhaps like this:

pass='my !@#%%^&amp; password'
pass=$(php -r "echo urlencode(\"$pass\");")
&gt;&gt;&gt; my+%21%40%23%25%25%5E%26+password