[Discuss-gnuradio] usrp_spectrum_sense.py does not warn if given frequency is invalid

[Timo Juhani Lindfors]

Hi,

usrp_spectrum_sense.py contains

if not self.set_freq(target_freq):
    print "Failed to set frequency to", target_freq 

but this does not seem to get triggered even if I use an obviously
invalid frequency:

$ ./gr-uhd/examples/python/usrp_spectrum_sense.py --args addr=ettus2.lan 
--samp-rate 20e3 2 3
linux; GNU C++ version 4.7.0; Boost_104900; UHD_003.004.002-0-unknown

Warning: this may have issues on some machines+Python version
combinations to seg fault due to the callback in bin_statitics.

-- Opening a USRP2/N-Series device...
-- Current recv frame size: 1472 bytes
-- Current send frame size: 1472 bytes

UHD Warning:
    The hardware does not support the requested RX sample rate:
    Target sample rate: 0.020000 MSps
    Actual sample rate: 0.195312 MSps
Using Volk machine: sse4_a_64_orc
gain = 18.25

If I print the tune result object I see

Target RF  Freq: 0.075002 (MHz)
Actual RF  Freq: 1097.342708 (MHz)

In UHD source code I see "//forget the warning when manual policy" that
takes effect since uhd.tune_request.POLICY_MANUAL is used.

Where should this be fixed?