errors: add ERR_DEBUGGER_STARTUP_ERROR

Author: Trott

doc/api/errors.md

@@ -1011,6 +1011,14 @@ added: REPLACEME
 
 An error occurred with the [debugger][].
 
+<a id="ERR_DEBUGGER_STARTUP_ERROR"></a>
+### `ERR_DEBUGGER_STARTUP_ERROR`
+<!-- YAML
+added: REPLACEME
+-->
+
+The [debugger][] timed out waiting for the required host/port to be free.
+
 <a id="ERR_DLOPEN_FAILED"></a>
 ### `ERR_DLOPEN_FAILED`
 <!-- YAML

lib/internal/errors.js

@@ -891,6 +891,7 @@ E('ERR_CRYPTO_SCRYPT_NOT_SUPPORTED', 'Scrypt algorithm not supported', Error);
 // Switch to TypeError. The current implementation does not seem right.
 E('ERR_CRYPTO_SIGN_KEY_REQUIRED', 'No key provided to sign', Error);
 E('ERR_DEBUGGER_ERROR', '%s', Error);
+E('ERR_DEBUGGER_STARTUP_ERROR', '%s', Error);
 E('ERR_DIR_CLOSED', 'Directory handle was closed', Error);
 E('ERR_DIR_CONCURRENT_OPERATION',
   'Cannot do synchronous work on directory handle with concurrent ' +