GN: update error message for invalid input_conversion.

tools/gn/input_conversion.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "tools/gn/input_conversion.h"
 
 #include <utility>
 
 #include "base/macros.h"
 #include "base/strings/string_split.h"
@@ skipping 122 matching lines @@
   if (input_conversion == "value")
     return ParseValueOrScope(settings, input, PARSE_VALUE, origin, err);
   if (input_conversion == "string")
     return Value(origin, input);
   if (input_conversion == "list lines")
     return ParseList(input, origin, err);
   if (input_conversion == "scope")
     return ParseValueOrScope(settings, input, PARSE_SCOPE, origin, err);
 
   *err = Err(original_input_conversion, "Not a valid input_conversion.",
-             "Have you considered a career in retail?");
+             "Run gn help input_conversion to see your options.");
   return Value();
 }
 
 }  // namespace
 
 extern const char kInputConversion_Help[] =
     "input_conversion: Specifies how to transform input to a variable.\n"
     "\n"
     "  input_conversion is an argument to read_file and exec_script that\n"
     "  specifies how the result of the read operation should be converted\n"
@@ skipping 50 matching lines @@
                           const ParseNode* origin,
                           const Value& input_conversion_value,
                           Err* err) {
   if (input_conversion_value.type() == Value::NONE)
     return Value();  // Allow null inputs to mean discard the result.
   if (!input_conversion_value.VerifyTypeIs(Value::STRING, err))
     return Value();
   return DoConvertInputToValue(settings, input, origin, input_conversion_value,
                                input_conversion_value.string_value(), err);
 }