do not use shellcheck and pyflakes executables at current directory

by using execabs.LookPath instead of exec.LookPath

context: sharkdp/bat#1724

example_test.go

@@ -4,12 +4,13 @@ import (
 	"bufio"
 	"io/ioutil"
 	"os"
-	"os/exec"
 	"path/filepath"
 	"regexp"
 	"sort"
 	"strings"
 	"testing"
+
+	"golang.org/x/sys/execabs"
 )
 
 func TestExamples(t *testing.T) {
@@ -51,15 +52,15 @@ func TestExamples(t *testing.T) {
 			opts := LinterOptions{}
 
 			if strings.Contains(testName, "shellcheck") {
-				p, err := exec.LookPath("shellcheck")
+				p, err := execabs.LookPath("shellcheck")
 				if err != nil {
 					t.Skip("skipped because \"shellcheck\" command does not exist in system")
 				}
 				opts.Shellcheck = p
 			}
 
 			if strings.Contains(testName, "pyflakes") {
-				p, err := exec.LookPath("pyflakes")
+				p, err := execabs.LookPath("pyflakes")
 				if err != nil {
 					t.Skip("skipped because \"pyflakes\" command does not exist in system")
 				}

go.mod

@@ -11,5 +11,6 @@ require (
 	github.com/mattn/go-runewidth v0.0.13
 	github.com/robfig/cron v1.2.0
 	golang.org/x/sync v0.0.0-20210220032951-036812b2e83c
+	golang.org/x/sys v0.0.0-20210630005230-0f9fa26af87c
 	gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b
 )

go.sum

@@ -22,8 +22,9 @@ github.com/robfig/cron v1.2.0/go.mod h1:JGuDeoQd7Z6yL4zQhZ3OPEVHB7fL6Ka6skscFHfm
 golang.org/x/sync v0.0.0-20210220032951-036812b2e83c h1:5KslGYwFpkhGh+Q16bwMP3cOontH8FOep7tGV86Y7SQ=
 golang.org/x/sync v0.0.0-20210220032951-036812b2e83c/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20200116001909-b77594299b42/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20200223170610-d5e6a3e2c0ae h1:/WDfKMnPU+m5M4xB+6x4kaepxRw6jWvR5iDRdvjHgy8=
 golang.org/x/sys v0.0.0-20200223170610-d5e6a3e2c0ae/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20210630005230-0f9fa26af87c h1:F1jZWGFhYfh0Ci55sIpILtKKK8p3i2/krTr0H1rg74I=
+golang.org/x/sys v0.0.0-20210630005230-0f9fa26af87c/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IVDexMakfv52eLZ2CXBWiKr4=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=

rule_pyflakes.go

@@ -8,6 +8,7 @@ import (
 	"sync"
 
 	"golang.org/x/sync/errgroup"
+	"golang.org/x/sys/execabs"
 )
 
 type shellIsPythonKind int
@@ -43,7 +44,7 @@ type RulePyflakes struct {
 // or relative/absolute file path. When the given executable is not found in system, it returns
 // an error.
 func NewRulePyflakes(executable string) (*RulePyflakes, error) {
-	p, err := exec.LookPath(executable)
+	p, err := execabs.LookPath(executable)
 	if err != nil {
 		return nil, err
 	}

rule_shellcheck.go

@@ -9,6 +9,7 @@ import (
 	"sync"
 
 	"golang.org/x/sync/errgroup"
+	"golang.org/x/sys/execabs"
 )
 
 type shellcheckError struct {
@@ -34,7 +35,7 @@ type RuleShellcheck struct {
 // or relative/absolute file path. When the given executable is not found in system, it returns an
 // error as 2nd return value.
 func NewRuleShellcheck(executable string) (*RuleShellcheck, error) {
-	p, err := exec.LookPath(executable)
+	p, err := execabs.LookPath(executable)
 	if err != nil {
 		return nil, err
 	}