Unit names passed to `systemctl isolate` are improperly mangled,  escaping the '@' character and hence making an invalid unit name.

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$ systemctl --user cat graphic@:0.target
# /home/operator/.config/systemd/user/graphic@.target
.include need-session@.target

[Unit]
Description=Graphical session %I
Requires=overall.target
AllowIsolate=yes

$ systemctl --user start graphic@:0.target

$ systemctl --user isolate graphic@:0.target
Failed to start graphic\x40:0.target: Operation refused, unit may not be isolated.
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Patch will be sent to the ML shortly.