Fix: Consistently create error messages

[localheinz]

This PR

• consistently uses sprintf() for creating error messages
• consistently uses single quotes instead of double quotes for error messages

Follows #170 (comment).

[bighappyface]

This one will be tricky. There are others messing with the error messaging:

#122
#142

While I am fine with sprintf I know others are not, and performance impacts are debatable in context of micro-optimization.

I think we need a few people in favor of this one to force the change in convention.

@GrahamCampbell @alecsammon @Maks3w @samkeen thoughts?

[localheinz]

@bighappyface

I'm happy to push #122 and #142 forward first!

@doits @onlinesid

What do you think, can you rebase your PRs?

[onlinesid]

@localheinz I have rebased my #142

[bighappyface]

Closing for now