Hi,

Described behaviour is reproduced for systemd-208(RHEL), systemd-215 and trunk(calculate linux).
However, I'm not sure if it is actually a bug, or just misconfiguration of services.
STR:
1) Create following unit files:
$ cat env@.target 
[Unit]
Description=Test Environment Target

[Install]
WantedBy=multi-user.target
$ cat serv@.service 
[Unit]
Description=Service which is part of environment
Requires=env@%i.target

[Service]
PIDFile=/root/test.pid
Type=forking
ExecStart=/usr/bin/python /root/test_service.py
Restart=on-failure
RestartSec=30
TimeoutStopSec=30
KillMode=process

[Install]
WantedBy=multi-user.target
WantedBy=env@%i.target

test_service.py is simple script, which emulates either a fine working daemon, or a daemon which fails to start:
$ cat /root/test_service.py 
#!/usr/bin/env python
import os
from time import sleep
if os.fork() != 0:
    os._exit(0)
os.setsid()
if os.fork() != 0:
    os._exit(0)
os.chdir('/')
## os._exit(2) ## uncomment to emulate failing daemon
pid_fo = open('/root/test.pid', 'w')
pid_fo.write(str(os.getpid()) + '\n')
pid_fo.close()
sleep(3600)

2) Enable target and service and start them:
systemctl enable serv@1.2.3.4
systemctl enable env@1.2.3.4.target
systemctl start env@1.2.3.4.target serv@1.2.3.4

3) Uncomment "os._exit(2)" and restart env@1.2.3.4.target:
time systemctl restart env@1.2.3.4.target

Expected result:
restart command should fail, as "systemctl restart serv@1.2.3.4" fails:
# systemctl restart serv@1.2.3.4
Job for serv@1.2.3.4.service failed. See "systemctl status serv@1.2.3.4.service" and "journalctl -xe" for details.

Actual result:
systemctl does not return:
# time systemctl restart env@1.2.3.4.target 
^C
real	16m0.964s
user	0m0.010s
sys	0m0.000s

Backtrace for systemd-208 systemctl:
#0  0x00007f3766cdeec0 in __poll_nocancel () at ../sysdeps/unix/syscall-template.S:81
#1  0x00007f3767ab7780 in socket_do_iteration () from /lib64/libdbus-1.so.3
#2  0x00007f3767ab65ff in _dbus_transport_do_iteration () from /lib64/libdbus-1.so.3
#3  0x00007f3767a9fd7c in _dbus_connection_do_iteration_unlocked () from /lib64/libdbus-1.so.3
#4  0x00007f3767aa2112 in _dbus_connection_read_write_dispatch () from /lib64/libdbus-1.so.3
#5  0x00007f3768112029 in start_unit ()
#6  0x00007f3768108ac5 in main ()

If serv@.service unit file is created without "Requires=env@%i.target", everything works just fine.