ANSI escapes for bold in tables headers are being sent even when output is not a terminal

[hindessm]

There was a bug introduced by 4befcee. ANSI escapes should only be output if stdout is a terminal. However, this line is causing ANSI escapes for bold to be added even if output is to a pipe or file. This is easy to reproduce/spot by piping any output that produces a table through od -c with the ANSI escapes starting with 033 octal ESC characters. Our plugin (eventstreams) produces tables with cells that have color, when stdout is not a terminal, the ANSI escapes for colors are correctly omitted but they are still being added to the headers.

[hindessm]

I can reproduce it with a simple example like:

package main

import (
        "github.com/IBM-Cloud/ibm-cloud-cli-sdk/bluemix/terminal"
)

func main() {
        ui := terminal.NewStdUI()
        table := ui.Table([]string{"Fruit"})
        table.Add("Apple")
        table.Print()
}

If I run this then I get 'Fruit' in bold and 'Apple' in cyan. If I set IBMCLOUD_COLOR=false then I still get Fruit in bold but 'Apple' is no longer in cyan. I would expect the ANSI escape characters for bold to also have been omitted.

Similarly, if I pipe the output though | cat I would expect both the bold and cyan escapes to be removed but only the cyan is removed and the bold remains.