Add check to catch #30 early with a helpful message

.gitignore

@@ -1,3 +1,5 @@
 /build/
 /data/
+/info/
 /vendor/
+/config.test.yml

src/Commands/Auto.php

@@ -6,6 +6,7 @@ use Amp\CoroutineResult;
 use Amp\File\FilesystemException;
 use Amp\Process;
 use Kelunik\Acme\AcmeException;
+use Kelunik\AcmeClient\ConfigException;
 use League\CLImate\Argument\Manager;
 use League\CLImate\CLImate;
 use Symfony\Component\Yaml\Exception\ParseException;
@@ -225,11 +226,47 @@ class Auto implements Command {
         $result = [];
 
         foreach ($paths as $path => $domains) {
+            if (is_numeric($path)) {
+                $message = <<<MESSAGE
+Your configuration has the wrong format. Received a numeric value as path name.
+
+This is most probably due to your "paths" value not being a map but a list instead.
+
+If your configuration looks like this:
+
+certificates:
+ - paths:
+    - /www/a: a.example.org
+    - /www/b: b.example.org
+
+Rewrite it to the following format for a single certificate:
+
+certificates:
+ - paths:
+     /www/a: a.example.org
+     /www/b: b.example.org
+
+Rewrite it to the following format for two separate certificates:
+
+certificates:
+ - paths:
+     /www/a: a.example.org
+ - paths:
+     /www/b: b.example.org
+
+Documentation is available at https://github.com/kelunik/acme-client/blob/master/doc/usage.md#configuration
+
+If this doesn't solve your issue, please reply to the following issue: https://github.com/kelunik/acme-client/issues/30
+MESSAGE;
+
+                throw new ConfigException($message);
+            }
+
             $domains = (array) $domains;
 
             foreach ($domains as $domain) {
                 if (isset($result[$domain])) {
-                    throw new \LogicException("Duplicate domain: {$domain}");
+                    throw new ConfigException("Duplicate domain: {$domain}");
                 }
 
                 $result[$domain] = $path;