utils.py: Fixing assertion in drange to allow equal inputs

[abhmul]

We should allow drange to allow the same input value for v0 and v1. In this case, drange will return an iterator of one element: v0 // d.

I ran into an issue when using Camelot, where the values passed into v0 and v1 were the same. The original assertion in drange will fail when values for v0 and v1 are the same. However, I don't see why they can't be the same. In this case, drange will return a range iterator with just a single element equal to v0 // d. Making this change fixed the assertion without any incorrect change in the output of my code.

I am not very familiar with the codebases of pdfminer or Camelot, so I'd like an active contributor to take a look and see if there are any obvious issues. In the meanwhile, I'll continue to do some more investigation to see if this change could pose a problem somewhere, and I'll update this PR with anything I find.

[pietermarsman]

This change would make drange different from the built-in range because the latter returns an empty list when the start and end are equal:

>>> list(range(0, 0))
[]

Changing drange the suggested way would be confusing since drange is obviously modelled after range().

Rather I would like drange to return an empty list if v0 <= v1 and d > 0.

[pietermarsman]

Hi @abhmul, your PR seems to be related to #66. Do you have time to work on this?

[pietermarsman]

I think this PR solves a problem in an unsatisfying manner.

drange should never throw an AssertionError when the inputs are wrong. It should return an empty list just like the builtin range.

@abhmul this is just a small change, can you do it?

[abhmul]

Sure, I can do it this week, should be a quick fix.

[pietermarsman]

I've checked and there is no except clause in pdfminer that catches a AssertionError. Thus the assertion can safely be replaced by returning an empty list like range does.