Include env var in validation error message

lib/convict.js

@@ -321,6 +321,11 @@ function normalizeSchema(name, node, props, fullName, env, argv, sensitive) {
       // attach the value and the property's fullName to the error
       e.fullName = fullName;
       e.value = x;
+
+      if (o.env) {
+        e.env = o.env;
+      }
+
       throw e;
     }
   };
@@ -648,7 +653,13 @@ let convict = function convict(def, opts) {
             let e = errors[i];
 
             if (e.fullName) {
-              err_buf += e.fullName + ': ';
+              err_buf += e.fullName;
+
+              if (e.env) {
+                err_buf += '[' + e.env + ']';
+              }
+
+              err_buf += ': ';
             }
             if (e.message) err_buf += e.message;
             if (e.value && !sensitive.has(e.fullName)) {

test/cases/env_syntax.out

@@ -1 +1 @@
-foo.bar: must be one of the possible values: ["a","b"]: value was "c"
+foo.bar[BAR]: must be one of the possible values: ["a","b"]: value was "c"