When using hwcert-backend behind a proxy, how can I exclude systems from beeing reached through the proxy?

Issue

• I use hwcert-backend behind a proxy, why do the following variables not disable the proxy to be used for 192.168.2.1?

NO_PROXY=localhost,127.0.0.0/8,192.168.2.0/24
http_proxy=http://10.0.0.1:3128/
no_proxy=localhost,127.0.0.0/8,192.168.2.0/24
HTTP_PROXY=http://10.0.0.1:318/

I still get this error:

# hwcert-backend run --test fv_core --server 192.168.2.1
mkdir -p /tmp/hwcert-fv_core-5tmwbC
cp -a fv_core.py Makefile /tmp/hwcert-fv_core-5tmwbC
Warning: Could not contact the hwcert server on 192.168.2.1
HTTP Error 503: Service Unavailable
Set server to 192.168.2.1 for  1 test(s)

Running the following tests:
fv_core                                                   
info                                                      

Test Verification Passed
chmod a+x ./fv_core.py
/proc/cpuinfo has vmx flag
Testing kvm virtualization
Starting libvirtd daemon: 
libvirtd is running
Verified that guest hwcert-x86_64 is not running
Note: /var/lib/libvirt/images/hwcertData.img not found, attempting download
--2013-09-10 10:04:36--  http://192.168.2.1/hwcert/fv-images/hwcertData.img.tar.bz2
Connecting to 10.0.0.1:3128... connected.
Proxy request sent, awaiting response... 

I need to use the proxy for internet connections, but nontheless 192.168.2.1 should be reached without proxy.