RadonBear: Handle col_offset==0 correctly

Radon uses visitor.col_offset as 0 for results where column is not
given. As we use None, we simply map it appropriately.
(As suggested by blueyed)

Fixes #609

bears/python/RadonBear.py

@@ -45,8 +45,9 @@ def run(self, filename, file,
             if severity is None:
                 continue
 
+            col = visitor.col_offset if visitor.col_offset else None
             visitor_range = SourceRange.from_values(
-                filename, visitor.lineno, visitor.col_offset, visitor.endline)
+                filename, visitor.lineno, col, visitor.endline)
             message = "{} has a cyclomatic complexity of {}".format(
                 visitor.name, rank)
 

tests/python/RadonBearTest.py

@@ -12,14 +12,21 @@ class class1():
     pass
 """
 
+test_file3 = "def f():\n" + ("    assert True\n" * 50)
 
-RadonBearNoReportsTest = verify_local_bear(
+
+RadonBearDefaultsTest = verify_local_bear(
     RadonBear,
     valid_files=(test_file1, test_file2),
-    invalid_files=(),
-    settings={"radon_ranks_info": "",
-              "radon_ranks_normal": "",
-              "radon_ranks_major": ""})
+    invalid_files=(test_file3,))
+
+
+RadonBearNoReportsTest = verify_local_bear(RadonBear,
+     valid_files=(test_file1, test_file2, test_file3),
+     invalid_files=(),
+     settings={"radon_ranks_info": "",
+               "radon_ranks_normal": "",
+               "radon_ranks_major": ""})
 
 
 RadonBearReportsTest = verify_local_bear(