tests: Make vhs use colors in its output

Colored output is useful both in CI and on local machines, because it
makes it a lot easier to find the error message in the vhs output.

By default vhs doesn't use colors if stdout is not a tty (which it is
not the way we are currenty executing it).

Author: adombeck

pam/integration-tests/vhs-helpers_test.go

@@ -243,6 +243,7 @@ func (td tapeData) RunVhs(t *testing.T, testType vhsTestType, outDir string, cli
 
 	cmd := exec.Command("env", "vhs")
 	cmd.Env = append(testutils.AppendCovEnv(cmd.Env), cliEnv...)
+	cmd.Env = append(cmd.Env, "CLICOLOR_FORCE=1")
 	cmd.Dir = outDir
 
 	// If vhs is installed with "go install", we need to add GOPATH to PATH.