Description of problem:
In WebUI, if a registered system has a package that is not on the Satellite, it can still be scheduled for removal. In API, however, I have not found a way to do this.

schedulePackageRemove requires package ID.
schedulePackageRemoveByNevra does not require package ID but still does not find the package (as it probably searches the database which does not contain it) and fails with (for antlr package):

Traceback (most recent call last):
  File "./z.py", line 9, in <module>
    res = client.system.schedulePackageRemoveByNevra(key,1000010001,[{'package_name': "antlr", 'package_epoch': "0", 'package_version': "2.7.7", 'package_release': "6.5.el6", 'package_arch': "x86_64"}], datetime.now())
  File "/usr/lib64/python2.6/xmlrpclib.py", line 1199, in __call__
    return self.__send(self.__name, args)
  File "/usr/lib64/python2.6/xmlrpclib.py", line 1489, in __request
    verbose=self.__verbose
  File "/usr/lib64/python2.6/xmlrpclib.py", line 1253, in request
    return self._parse_response(h.getfile(), sock)
  File "/usr/lib64/python2.6/xmlrpclib.py", line 1392, in _parse_response
    return u.close()
  File "/usr/lib64/python2.6/xmlrpclib.py", line 838, in close
    raise Fault(**self._stack[0])
xmlrpclib.Fault: <Fault 2300: 'redstone.xmlrpc.XmlRpcFault: Invalid package: antlr'>


How reproducible:
Deterministic

Steps to Reproduce:
For an existing system with antlr-2.7.7-6.5.el6:0 package installed and not synced to satellite, in python:
client.system.schedulePackageRemoveByNevra(key,<SYSTEMID>,[{'package_name': "antlr", 'package_epoch': "0", 'package_version': "2.7.7", 'package_release': "6.5.el6", 'package_arch': "x86_64"}], datetime.now())

Actual results:
Nothing scheduled, traceback

Expected results:
Package removal scheduled

Additional info:
This operation can be done using WebUI so I think it should also be possible using API