More graceful handling of low linewrap values (#1219)

* behavior outline

* enforce positive initial linewrap

Check column widths

update gitignore

throw error when linewrap too small

simply check for large enough linewrap value

* delete unused error message

* PR feedback

make exception more informative

update check_linewrap signature in src and test

make check_linewrap a free function

* delete unused function

* delete else..pass block

* newline for make format

features/steps/export_steps.py

@@ -12,6 +12,14 @@ from behave import given
 from behave import then
 
 
+@then("the output should be {width:d} columns wide")
+def check_output_width(context, width):
+    out = context.stdout_capture.getvalue()
+    out_lines = out.splitlines()
+    for line in out_lines:
+        assert len(line) <= width
+
+
 @then("the output should be parsable as json")
 def check_output_json(context):
     out = context.stdout_capture.getvalue()