aptdaemon cannot import key when buying a software in software-center behind a (simple) proxy

Whan you try to Buy a software from the software center , it fails at importing the corresponding the keyring and thus never start to download and install the package.

the problem seems to be with gpg that does not use the http_proxy to retrive the key , the error returned is like :

""
Failed to download and install the key 0x33E0E91BDD8E7F4B53837F09E131728675254D99 from hkp://keyserver.ubuntu.com:80/:
gpg: keyring `/tmp/tmpfrWWtz/secring.gpg' created
gpg: keyring `/tmp/tmpfrWWtz/pubring.gpg' created
gpg: requesting key 75254D99 from hkp server keyserver.ubuntu.com
gpg: keyserver timed out
gpg: keyserver receive failed: keyserver error
Traceback (most recent call last):
  File "/usr/share/aptdaemon/aptd-import-from-keyserver", line 98, in <module>
    add_key_from_keyserver(keyid, keyserver)
  File "/usr/share/aptdaemon/aptd-import-from-keyserver", line 23, in add_key_from_keyserver
    _add_key_from_keyserver(keyid, keyserver, tmp_keyring_dir)
  File "/usr/share/aptdaemon/aptd-import-from-keyserver", line 51, in _add_key_from_keyserver
    keyserver, keyid))
__main__.AptKeyError: recv from 'hkp://keyserver.ubuntu.com:80/' failed for '0x33E0E91BDD8E7F4B53837F09E131728675254D99'
"""

How to reproduce :

- Install ubuntu 12.04.3 64 bits

- Configure a simple http_proxy http://server:port in the proxy preferences of the system

- Try to install IntelliJidea from the Software center

- And error message is displayed about the error downloading the keyring , click OK

- Thus an error message is displayed saying that the packages will be unanthenticated. clicking repair won't fix the problem as you would expect.