test: skip networked tests if no connection (#661)

* test: skip networked tests if no connection

* fix: handle unexpected http responses

* fix: return if a valid URL is generated

* test: delete networked test

glow_test.go

@@ -1,33 +1,9 @@
 package main
 
 import (
-	"bytes"
 	"testing"
 )
 
-func TestGlowSources(t *testing.T) {
-	tt := []string{
-		".",
-		"README.md",
-		"github.com/charmbracelet/glow",
-		"github://charmbracelet/glow",
-		"https://github.com/charmbracelet/glow",
-	}
-
-	for _, v := range tt {
-		t.Run(v, func(t *testing.T) {
-			buf := &bytes.Buffer{}
-			err := executeArg(rootCmd, v, buf)
-			if err != nil {
-				t.Errorf("Error during execution (args: %s): %v", v, err)
-			}
-			if buf.Len() == 0 {
-				t.Errorf("Output buffer should not be empty (args: %s)", v)
-			}
-		})
-	}
-}
-
 func TestGlowFlags(t *testing.T) {
 	tt := []struct {
 		args  []string