go/packages: detect missing binary via exec.ErrNotFound error

exec.Command already runs exec.LookPath when given a name that contains
no path separators. There's no need to call exec.LookPath a second time
to detect that cmd.Run failed because of a missing executable file.
It can be detected from the returned error. Do so because it's cleaner.

Also improve the error text to say that the problem was that the go
executable file was not found in $PATH (or %PATH%, etc., depending on
the underlying operating system). In the general case, we can't know if
Go is or isn't installed.

Example error text on macOS:

	gopackages: 'go list' driver requires 'go', but executable file not found in $PATH

Updates golang/go#29552

Change-Id: I769553f125240dccd02098c22641f6a1ed10063c
Reviewed-on: https://go-review.googlesource.com/c/tools/+/168897
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Matloob <matloob@golang.org>
1 file changed
tree: defb89073eece6231257d2b025b367b2b537e8c2
  1. .gitattributes
  2. .gitignore
  3. AUTHORS
  4. CONTRIBUTING.md
  5. CONTRIBUTORS
  6. LICENSE
  7. PATENTS
  8. README.md
  9. benchmark/
  10. blog/
  11. cmd/
  12. codereview.cfg
  13. container/
  14. cover/
  15. go.mod
  16. go.sum
  17. go/
  18. godoc/
  19. imports/
  20. internal/
  21. playground/
  22. present/
  23. refactor/
README.md

Go Tools

This subrepository holds the source for various packages and tools that support the Go programming language.

Some of the tools, godoc and vet for example, are included in binary Go distributions.

Others, including the Go guru and the test coverage tool, can be fetched with go get.

Packages include a type-checker for Go and an implementation of the Static Single Assignment form (SSA) representation for Go programs.

Download/Install

The easiest way to install is to run go get -u golang.org/x/tools/.... You can also manually git clone the repository to $GOPATH/src/golang.org/x/tools.

Report Issues / Send Patches

This repository uses Gerrit for code changes. To learn how to submit changes to this repository, see https://golang.org/doc/contribute.html.

The main issue tracker for the tools repository is located at https://github.com/golang/go/issues. Prefix your issue with “x/tools/(your subdir):” in the subject line, so it is easy to find.