fix: Add message for Reddit 403 response

When Reddit API responds with error, the body may be formatted as
HTML and contains details about the problem.

reddit.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"net/url"
 
+	"github.com/macie/opinions/html"
 	"github.com/macie/opinions/http"
 )
 
@@ -55,6 +56,17 @@ func SearchReddit(ctx context.Context, client http.Client, query string) ([]Disc
 			return discussions, fmt.Errorf("cannot search Reddit: too many requests. Wait %s seconds", r.Header.Get("X-Ratelimit-Reset"))
 		}
 
+		if r.StatusCode == 403 {
+			var details string
+			body, err := html.Parse(r.Body)
+			if err != nil {
+				details = ""
+			}
+			details = html.Text(html.First(body, "p"))
+
+			return discussions, fmt.Errorf("cannot search Reddit: your IP address seems to be banned by Reddit: `GET %s` responded with `%s`", r.Request.URL, details)
+		}
+
 		return discussions, fmt.Errorf("cannot search Reddit: `GET %s` responded with status code %d", r.Request.URL, r.StatusCode)
 	}