Add "module" estimator spec

Import a (possibly local) module and look for a global named `estimator`

osprey/config.py

@@ -44,7 +44,7 @@
 
 FIELDS = {
     'estimator':       ['pickle', 'eval', 'eval_scope', 'entry_point',
-                        'params'],
+                        'params', 'module'],
     'dataset_loader':  ['name', 'params'],
     'trials':          ['uri', 'project_name'],
     'search_space':    dict,
@@ -149,7 +149,18 @@ def estimator(self):
             pickle: path-to-pickle-file.pkl
             eval: "Pipeline([('cluster': KMeans())])"
             entry_point: sklearn.linear_model.LogisticRegression
+            module: myestimator
         """
+        module_path = self.get_value('estimator/module')
+        if module_path is not None:
+            with prepend_syspath(dirname(abspath(self.path))):
+                estimator_module = importlib.import_module(module_path)
+            estimator = estimator_module.estimator()
+            if not isinstance(estimator, sklearn.base.BaseEstimator):
+                raise RuntimeError('estimator/pickle must load a '
+                                   'sklearn-derived Estimator')
+            return estimator
+
         evalstring = self.get_value('estimator/eval')
         if evalstring is not None:
             got = self.get_value('estimator/eval_scope')
@@ -166,7 +177,8 @@ def estimator(self):
                     scope.update(getattr(eval_scopes, pkg_name)())
                 else:
                     try:
-                        pkg = importlib.import_module(pkg_name)
+                        with prepend_syspath(dirname(abspath(self.path))):
+                            pkg = importlib.import_module(pkg_name)
                     except ImportError as e:
                         raise RuntimeError(str(e))
                     scope.update(eval_scopes.import_all_estimators(pkg))