net/url: improve url parsing error messages by quoting
Current implementation doesn't always make it obvious what the exact
problem with the URL is, so this makes it clearer by consistently quoting
the invalid URL, as is the norm in other parsing implementations, eg.:
strconv.Atoi(" 123") returns an error: parsing " 123": invalid syntax
Updates #29261
Change-Id: Icc6bff8b4a4584677c0f769992823e6e1e0d397d
GitHub-Last-Rev:
648b9d93fe149ec90f3aeca73019158a344de03e
GitHub-Pull-Request: golang/go#29384
Reviewed-on: https://go-review.googlesource.com/c/go/+/185117
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>