Improves error handling when "shear" but no metadata passed

Makefile

@@ -27,7 +27,7 @@ jstest:
 stylecheck:
 	jshint $(JSLOCS)
 	prettier --check --tab-width 4 $(JSLOCS) $(CSSLOCS)
-	flake8 empress/*.py tests/python/*.py setup.py
+	flake8 empress/*.py tests/python/*.py setup.py empress/scripts/*.py
 
 # Auto-formats the JS code
 jsstyle:

empress/core.py

@@ -136,6 +136,11 @@ def __init__(self, tree, table=None, sample_metadata=None,
             # self._validate_and_match_data()
             self.features = feature_metadata.copy()
         else:
+            if shear_to_feature_metadata:
+                raise ValueError(
+                    "Feature metadata must be provided in order to shear "
+                    "to feature metadata."
+                )
             self.features = None
 
         self.ordination = ordination

empress/scripts/_cli.py

@@ -15,10 +15,12 @@ def empress():
     """Generates an interactive visualization of a phylogenetic tree."""
     pass
 
+
 # Allow using -h to show help information
 # https://click.palletsprojects.com/en/7.x/documentation/#help-parameter-customization
 CTXSETS = {"help_option_names": ["-h", "--help"]}
 
+
 @empress.command(
     "tree-plot", short_help=desc.TREE_PLOT_DESC, context_settings=CTXSETS
 )

tests/python/test_core.py

@@ -204,6 +204,11 @@ def test_init_tree_plot_fm_not_matching(self):
         ):
             Empress(self.tree, feature_metadata=bad_fm)
 
+    def test_init_tree_plot_shear_without_metadata(self):
+        with self.assertRaisesRegex(ValueError,
+                                    "Feature metadata must be provided"):
+            Empress(self.tree, shear_to_feature_metadata=True)
+
     def test_init_only_one_of_table_and_sm_passed(self):
         exp_errmsg = (
             "Both the table and sample metadata should be specified or None. "