Attempt to fix the fit in the presence of upper limit. For some reason the...

Attempt to fix the fit in the presence of upper limit. For some reason the newton method sometimes does not converge. Patch by Denis Burgarella.

pcigale/analysis_modules/pdf_analysis/workers.py

@@ -261,10 +261,9 @@ def analysis(idx, obs):
 
     if lim_flag == True:
         for imod in range(len(model_fluxes)):
-            norm_facts[imod] = optimize.newton(dchi2_over_ds2,
-                                               norm_facts[imod], tol=1e-16,
+            norm_facts[imod] = optimize.root(dchi2_over_ds2, norm_facts[imod],
                                                args=(obs_fluxes, obs_errors,
-                                                     model_fluxes[imod, :]))
+                                                     model_fluxes[imod, :])).x
     model_fluxes *= norm_facts[:, np.newaxis]
 
     # χ² of the comparison of each model to each observation.