new error messages for missing file and incorrect JSON formatting

taxcalc/parameters.py

@@ -693,16 +693,18 @@ def convert_year_to_int(syr_dict):
             txt = req.text
         else:
             if isinstance(topkey, str) and (topkey == ''):
-                raise ValueError("String is empty.")
+                raise ValueError("topkey string is empty.")
             if isinstance(obj, str):
                 if obj == '':
-                    raise ValueError("String is empty.")    
+                    raise ValueError("obj string is empty.")    
+                elif obj.endswith('.json') and not os.path.isfile(obj):
+                    raise FileNotFoundError("The .json file does not exist.")
                 elif ("{" and "}") in obj:
                     txt = obj
                 else:
-                    raise OSError("The .json file or variable does not exist or is misspecified.")
+                    raise ValueError("The JSON variable is misspecified.")
             else:
-                raise OSError("The .json file or variable does not exist or is misspecified.")
+                raise ValueError("The JSON variable is misspecified.")
         # strip out //-comments without changing line numbers
         json_txt = re.sub('//.*', ' ', txt)
         # convert JSON text into a Python dictionary

taxcalc/tests/test_calculator.py

@@ -504,7 +504,7 @@ def test_read_bad_json_assump_file():
     """
     with pytest.raises(ValueError):
         Calculator.read_json_param_objects(None, badassump1)
-    with pytest.raises(OSError):
+    with pytest.raises(ValueError):
         Calculator.read_json_param_objects(None, 'unknown_file_name')
     with pytest.raises(ValueError):
         Calculator.read_json_param_objects(None, list())
@@ -514,9 +514,9 @@ def test_json_doesnt_exist():
     """
     Test JSON file which doesn't exist
     """
-    with pytest.raises(OSError):
+    with pytest.raises(FileNotFoundError):
         Calculator.read_json_param_objects(None, './reforms/doesnt_exist.json')
-    with pytest.raises(OSError):
+    with pytest.raises(FileNotFoundError):
         Calculator.read_json_param_objects('./reforms/doesnt_exist.json', None)