DOC: Missing blankspace in error message raised by cont2discrete()

[budjen-jovan]

Issue with current documentation:

At the end of the function, the error raised is

raise ValueError("Impulse method is only applicable"
                          "to strictly proper systems")

which as a result misses a whitespace between applicable and to

Idea or request for content:

Looking at the way other errors are being raised in the same function, I suggest adding a whitespace at the end of the first string, i.e.

raise ValueError("Impulse method is only applicable "
                          "to strictly proper systems")

Additional context (e.g. screenshots, GIFs)

I'm not sure if this falls under documentation exactly, but it's the closest to what this is, please do let me know if there is an intended way to report this.