Phergie currently uses :IDENTIFY <nick> <password> to identify to nickserv. Which means the bot will try to identify with its current nick. As you can see below having the bot's nick in the identify command is for identifying with a different nick than the one the bot is currently using. On top of that Rizon does not account for identifying for a different nick than the current nick and all IDENTIFY commands fail on Rizon. I'm sure there are other networks that expect such behavior.

Since :IDENTIFY <password> is the common denominator Phergie should use that format or allow the format to be specified by the user.

Espernet:

NickServ: ***** NickServ Help *****
NickServ: Help for IDENTIFY:
NickServ:
NickServ: IDENTIFY identifies you with services so that you
NickServ: can perform general maintenance and commands that
NickServ: require you to be logged in.
NickServ:
NickServ: Syntax: IDENTIFY <password>
NickServ:
NickServ: You can also identify for another nick than you
NickServ: are currently using.
NickServ:
NickServ: Syntax: IDENTIFY <nick> <password>
NickServ:
NickServ: Example:
NickServ: /msg NickServ IDENTIFY foo
NickServ: /msg NickServ IDENTIFY jilles foo
NickServ: ***** End of Help *****

Freenode:

NickServ: ***** NickServ Help *****
NickServ: Help for IDENTIFY:
NickServ:
NickServ: IDENTIFY identifies you with services so that you
NickServ: can perform general maintenance and commands that
NickServ: require you to be logged in.
NickServ:
NickServ: Syntax: IDENTIFY <password>
NickServ:
NickServ: You can also identify for another nick than you
NickServ: are currently using.
NickServ:
NickServ: Syntax: IDENTIFY <nick> <password>
NickServ:
NickServ: Example:
NickServ: /msg NickServ IDENTIFY foo
NickServ: /msg NickServ IDENTIFY jilles foo
NickServ: ***** End of Help *****

Rizon:

help identify
NickServ: Syntax: IDENTIFY password
NickServ:
NickServ: Tells NickServ that you are really the owner of this
NickServ: nick. Many commands require you to authenticate yourself
NickServ: with this command before you use them. The password
NickServ: should be the same one you sent with the REGISTER
NickServ: command.

There are instances where it is desirable for other plugins to be aware of when authentication with NickServ is successful, such as joining channels that require user registration. Modify handleNick() to emit a custom event that other plugins can listen for.

Only when the nickname is in use I get the following error, on other conditions the script works.

"PHP Catchable fatal error: Argument 1 passed to Phergie\Irc\Plugin\React\NickServ\Plugin::handleNicknameInUse() must implement interface Phergie\Irc\Event\UserEventInterface, instance of Phergie\Irc\Event\ServerEvent given in /home//dev/vendor/phergie/phergie-irc-plugin-react-nickserv/src/Plugin.php on line 140"

See this page for more information.

This should only require setting a 'local_cert' context option referencing the path to the appropriate certificate file for the connection socket to use.

Just a heads up, this plugin seems to be missing from packagist, thus is unavailable through composer. The plugin is working fine for me after manually copying, but this may deter other users.

Cheers!

Some networks are more verbose with their NickServ challenge. Removing the period from the regexp would make the plugin a tad more flexible.
https://github.com/phergie/phergie-irc-plugin-react-nickserv/blob/master/src/Plugin.php#L91