object_usage_linter() should set useFancyQuotes=FALSE

[MichaelChirico]

Compare:

str <- "foo <- function() {\n  x\n}\n"

options(useFancyQuotes = FALSE)
lintr::lint(text = str, linters = lintr::object_usage_linter())
# <text>:2:3: warning: [object_usage_linter] no visible binding for global variable 'x'.
#   x
#   ^
options(useFancyQuotes = TRUE)
lintr::lint(text = str, linters = lintr::object_usage_linter())
# <text>:2:3: warning: [object_usage_linter] no visible binding for global variable ‘x’.
#   x
#   ^

I think we should follow suit of testthat and turn off quotes here -- makes the lint appear differently depending on global options & it's harder to manipulate the message with non-ASCII characters.

The fix is pretty trivial to implement; filing here first as a gut check that this is the right approach.

[AshesITR]

I don't see an issue with using fancy quotes here, since the lint message is meant to be read by a user.

We can't guarantee ASCII messages anyway since the messages can contain arbitrary parts of user code.

[MichaelChirico]

That's basically right, but it's still something in our control that allows us to be more consistent. I don't think we use fancy quotes in any messages generated by us. And the fix is one line (wrap codetools call with with_options(list(useFancyQuotes = FALSE), ...))