raco pkg: improve error for failed package-source download

Related to PR 14441

racket/collects/pkg/lib.rkt

@@ -140,7 +140,14 @@
         (λ (op)
           (call/input-url+200
            url
-           (λ (ip) (copy-port ip op))))))
+           (λ (ip) (copy-port ip op))
+           #:failure
+           (lambda (reply-s)
+             (pkg-error (~a "error downloading package\n"
+                            "  URL: ~a\n"
+                            "  server response: ~a")
+                        (url->string url)
+                        (read-line (open-input-string reply-s))))))))
     (cond
      [(and checksum use-cache?)
       (cache-file file

racket/collects/pkg/util.rkt

@@ -32,15 +32,18 @@
                 (make-string (+ (- width (string-length col)) 4) #\space))))
     (printf "\n")))
 
-(define (call/input-url+200 u fun #:headers [headers '()])
+(define (call/input-url+200 u fun
+                            #:headers [headers '()]
+                            #:failure [fail-k (lambda (s) #f)])
   #;(printf "\t\tReading ~a\n" (url->string u))
   (define-values (ip hs) (get-pure-port/headers u headers
                                                 #:redirections 25
                                                 #:status? #t))
-  (and (string=? "200" (substring hs 9 12))
+  (if (string=? "200" (substring hs 9 12))
       (begin0
        (fun ip)
-        (close-input-port ip))))
+       (close-input-port ip))
+      (fail-k hs)))
 
 (define (url-path/no-slash url)
   (define p (url-path url))