Merge branch 'fix_pymultinest' into 'master'

Resolve "CI failing on sampler tests"

Closes #459

See merge request lscsoft/bilby!723

bilby/core/sampler/pymultinest.py

@@ -81,6 +81,10 @@ class Pymultinest(NestedSampler):
                 .format(self.kwargs['outputfiles_basename']))
         check_directory_exists_and_if_not_mkdir(
             self.kwargs['outputfiles_basename'])
+
+        # for PyMultiNest >=2.9 the n_params kwarg cannot be None
+        if self.kwargs["n_params"] is None:
+            self.kwargs["n_params"] = self.ndim
         NestedSampler._verify_kwargs_against_default_kwargs(self)
 
     def _apply_multinest_boundaries(self):

test/sampler_test.py

@@ -481,7 +481,7 @@ class TestPymultinest(unittest.TestCase):
         expected = dict(importance_nested_sampling=False, resume=True,
                         verbose=True, sampling_efficiency='parameter',
                         outputfiles_basename='outdir/pm_label/',
-                        n_live_points=500, n_params=None,
+                        n_live_points=500, n_params=2,
                         n_clustering_params=None, wrapped_params=None,
                         multimodal=True, const_efficiency_mode=False,
                         evidence_tolerance=0.5,
@@ -497,7 +497,7 @@ class TestPymultinest(unittest.TestCase):
         expected = dict(importance_nested_sampling=False, resume=True,
                         verbose=True, sampling_efficiency='parameter',
                         outputfiles_basename='outdir/pm_label/',
-                        n_live_points=123, n_params=None,
+                        n_live_points=123, n_params=2,
                         n_clustering_params=None, wrapped_params=None,
                         multimodal=True, const_efficiency_mode=False,
                         evidence_tolerance=0.5,