Idiomatic rust organizes unit tests into `mod tests { }` blocks
using conditional compilation `[cfg(test)]` to decide whether to
compile the code in that block.
This commit moves "bare" test functions into such blocks, and puts
the block at the bottom of respective file.
It turns out Headers is actually an internal-only API. None of the
user-facing types use it.
Unfortunately, making it unexported also required deleting the doctests,
since doctests can only run against a public interface.
This adds a source field to keep track of upstream errors and allow
backtraces, plus a URL field to indicate what URL an error was
associated with.
The enum variants we used to use for Error are now part of a new
ErrorKind type. For convenience within ureq, ErrorKinds can be turned
into an Error with `.new()` or `.msg("some additional information")`.
Error acts as a builder, so additional information can be added after
initial construction. For instance, we return a DnsFailed error when
name resolution fails. When that error bubbles up to Request's
`do_call`, Request adds the URL.
Fixes#232.
This adds validation of header values on receive, and of both header
names and header values on send. This doesn't change the return
type of set to be a Result, it just validates when the request is
sent. Also removes the section in the README describing handling
of invalid headers, and updates a test that verified acceptance of
non-ASCII headers so that it verifies rejection of them instead.
