Data Race github.com/juju/juju/environs/tools/build.g

As seen in this example:
    http://reports.vapour.ws/releases/3926/job/run-unit-tests-race/attempt/1374#highlight

Goroutine 4 (running) created at:
  os/exec.(*Cmd).Start()
      /usr/lib/go/src/pkg/os/exec/exec.go:278 +0xfc9
  os/exec.(*Cmd).Run()
      /usr/lib/go/src/pkg/os/exec/exec.go:230 +0x34
  github.com/juju/juju/environs/tools.getVersionFromJujud()
      /home/ubuntu/juju-core_2.0-beta7/src/github.com/juju/juju/environs/tools/build.go:263 +0x4e0
  github.com/juju/juju/environs/tools_test.(*buildSuite).TestGetVersionFromJujud()
      /home/ubuntu/juju-core_2.0-beta7/src/github.com/juju/juju/environs/tools/build_test.go:155 +0x1d2
  runtime.call16()
      /usr/lib/go/src/pkg/runtime/asm_amd64.s:338 +0x31
  reflect.Value.Call()
      /usr/lib/go/src/pkg/reflect/value.go:345 +0xaa
  gopkg.in/check%2ev1.func·003()
      /home/ubuntu/juju-core_2.0-beta7/src/gopkg.in/check.v1/check.go:772 +0x504
  gopkg.in/check%2ev1.func·001()
      /home/ubuntu/juju-core_2.0-beta7/src/gopkg.in/check.v1/check.go:666 +0xf3