Fix #1336 - Print a friendly message when using invalid function names for fixers

autoload/ale/fix.vim

@@ -392,7 +392,13 @@ function! s:GetCallbacks() abort
             endif
         endif
 
-        call add(l:corrected_list, ale#util#GetFunction(l:Item))
+        try
+            call add(l:corrected_list, ale#util#GetFunction(l:Item))
+        catch /E475/
+            " Rethrow exceptions for failing to get a function so we can print
+            " a friendly message about it.
+            throw 'BADNAME ' . v:exception
+        endtry
     endfor
 
     return l:corrected_list
@@ -427,7 +433,7 @@ function! ale#fix#Fix(...) abort
 
     try
         let l:callback_list = s:GetCallbacks()
-    catch /E700/
+    catch /E700\|BADNAME/
         let l:function_name = join(split(split(v:exception, ':')[3]))
         let l:echo_message = printf(
         \   'There is no fixer named `%s`. Check :ALEFixSuggest',

test/fix/test_ale_fix.vader

@@ -574,6 +574,16 @@ Execute(ALE should print a message telling you something isn't a valid fixer whe
 
   AssertEqual 'There is no fixer named `invalidname`. Check :ALEFixSuggest', GetLastMessage()
 
+Execute(ALE should complain about invalid fixers with minuses in the name):
+  let g:ale_fixers.testft = ['foo-bar']
+  ALEFix
+
+  AssertEqual 'There is no fixer named `foo-bar`. Check :ALEFixSuggest', GetLastMessage()
+
+Execute(ALE should tolerate valid fixers with minuses in the name):
+  let g:ale_fixers.testft = ['prettier-standard']
+  ALEFix
+
 Execute(Test fixing with chained callbacks):
   let g:ale_fixers.testft = ['FirstChainCallback']
   ALEFix