Problems interpretting ~

When the config-file is set as "--config-file=~/etc/file.conf" then the following exception is received. Tried this with Quantum and glance.

Copenstack@openstack:/opt/stack/quantum$ cd /opt/stack/quantum && python /opt/stack/quantum/bin/quantum-server --config-file=~/etc/quantum.conf
Traceback (most recent call last):
File "/opt/stack/quantum/bin/quantum-server", line 24, in <module>
server()
File "/opt/stack/quantum/quantum/server/__init__.py", line 34, in main
config.parse(sys.argv)
File "/opt/stack/quantum/quantum/common/config.py", line 49, in parse
version='%%prog %s' % version_string())
File "/opt/stack/quantum/quantum/openstack/common/cfg.py", line 981, in __call__
self._parse_config_files()
File "/opt/stack/quantum/quantum/openstack/common/cfg.py", line 1403, in _parse_config_files
raise ConfigFilesNotFoundError(not_read_ok)
quantum.openstack.common.cfg.ConfigFilesNotFoundError: Failed to read some config files: ~/etc/quantum.conf
openstack@openstack:/opt/stack/quantum$

Note that if the = is removed then this works.