Update stub error messages (#434)

Author: BNAndras

exercises/practice/accumulate/accumulate.rkt

@@ -3,4 +3,4 @@
 (provide accumulate)
 
 (define (accumulate sequence operation)
-  (error "Not implemented yet"))
+  (error "Please implement 'accumulate'"))

exercises/practice/acronym/acronym.rkt

@@ -3,4 +3,4 @@
 (provide acronym)
 
 (define (acronym string)
-  (error "Not implemented yet"))
+  (error "Please implement 'acronym'"))

exercises/practice/affine-cipher/affine-cipher.rkt

@@ -1,4 +1,5 @@
-#lang racket/base
+#lang racket
+
 (require racket/contract)
 
 (provide (contract-out
@@ -10,7 +11,7 @@
                    exact-nonnegative-integer? . -> . string?)]))
 
 (define (encode msg a b)
-  (error "Not implemented yet"))
+  (error "Please implement 'encode'"))
 
 (define (decode msg a b)
-  (error "Not implemented yet"))
+  (error "Please implement 'decode'"))

exercises/practice/all-your-base/all-your-base.rkt

@@ -3,4 +3,4 @@
 (provide rebase)
 
 (define (rebase list-digits in-base out-base)
-  (error "Not implemented yet"))
+  (error "Please implement rebase"))

exercises/practice/allergies/allergies.rkt

@@ -3,7 +3,7 @@
 (provide list-allergies allergic-to?)
 
 (define (list-allergies score)
-  (error "Not implemented yet"))
+  (error "Please implement 'list-allergies'"))
 
 (define (allergic-to? str score)
-  (error "Not implemented yet"))
+  (error "Please implement 'allergic-to?'"))

exercises/practice/alphametics/alphametics.rkt

@@ -3,4 +3,4 @@
 (provide solve)
 
 (define (solve puzzle)
-  (error "Not implemented yet"))
+  (error "Please implement 'solve'"))

exercises/practice/anagram/anagram.rkt

@@ -3,4 +3,4 @@
 (provide anagrams-for)
 
 (define (anagrams-for subject candidates)
-  (error "Not implemented yet"))
+  (error "Please implement 'anagrams-for'"))

exercises/practice/armstrong-numbers/armstrong-numbers.rkt

@@ -3,4 +3,4 @@
 (provide armstrong-number?)
 
 (define (armstrong-number? n)
-  (error "Not implemented yet"))
+  (error "Please implement 'armstrong-number?'"))

exercises/practice/atbash-cipher/atbash-cipher.rkt

@@ -3,7 +3,7 @@
 (provide encode decode)
 
 (define (encode m)
-  (error "Not implemented yet"))
+  (error "Please implement 'encode'"))
 
 (define (decode m)
-  (error "Not implemented yet"))
+  (error "Please implement 'decode'"))

exercises/practice/bank-account/bank-account.rkt

@@ -4,4 +4,4 @@
 
 (define bank-account%
   (class object%
-    (error "Not implemented yet")))
+    (error "Please implement 'bank-account'")))