Resolve "Follow-up from "Adding dnest4 Sampler""

Requires !888 (merged) Closes #533 (closed)

bilby/core/sampler/base_sampler.py

 from __future__ import absolute_import
 import datetime
+import distutils.dir_util
 import numpy as np
+import os
+import tempfile
 
 from pandas import DataFrame
 
-from ..utils import logger, command_line_args, Counter
+from ..utils import logger, check_directory_exists_and_if_not_mkdir, command_line_args, Counter
 from ..prior import Prior, PriorDict, DeltaFunction, Constraint
 from ..result import Result, read_in_result
 
@@ -602,6 +605,27 @@ class NestedSampler(Sampler):
             return np.nan_to_num(-np.inf)
 
 
+def setup_run_directory(use_temporary_directory, outputfiles_basename):
+    """
+    Run directory setup for Dnest4 and Pymultinest.
+
+    If using a temporary directory, the output directory is moved to the
+    temporary directory.
+    """
+    if use_temporary_directory:
+        temporary_outputfiles_basename = tempfile.TemporaryDirectory().name
+
+        if os.path.exists(outputfiles_basename):
+            distutils.dir_util.copy_tree(outputfiles_basename, temporary_outputfiles_basename)
+        check_directory_exists_and_if_not_mkdir(temporary_outputfiles_basename)
+        logger.info("Using temporary file {}".format(temporary_outputfiles_basename))
+        return temporary_outputfiles_basename
+    else:
+        check_directory_exists_and_if_not_mkdir(outputfiles_basename)
+        logger.info("Using output file {}".format(outputfiles_basename))
+        return outputfiles_basename
+
+
 class MCMCSampler(Sampler):
     nwalkers_equiv_kwargs = ['nwalker', 'nwalkers', 'draws', 'Niter']
     nburn_equiv_kwargs = ['burn', 'nburn']