gstlal_inspiral_injection_snr: allowing user to not specify flow

gstlal-inspiral/bin/gstlal_inspiral_injection_snr

@@ -33,6 +33,7 @@ __author__ = 'Ryan Lang <ryan.lang@ligo.org>'
 
 import math
 import numpy
+import warnings
 
 from optparse import OptionParser
 from ligo import segments
@@ -64,7 +65,7 @@ def parse_command_line():
                 raise ValueError("Must specify --injection-file")
 
         if options.flow is None:
-                raise ValueError("Must specify --flow")
+                warnings.warn("No --flow specified. Will read from f_lower column of sim_inspiral table.")
 
         return options, filenames
 
@@ -102,7 +103,10 @@ def calc_expected_snr(inj):
                 f_min = inj.f_lower
         else:
                 LALparams = None
-                f_min = options.flow
+                if options.flow is None:
+                        f_min = inj.f_lower
+                else:
+                        f_min = options.flow
         
         h_plus, h_cross = lalsimulation.SimInspiralTD(
                 m1 = inj.mass1*lal.MSUN_SI,