Let's Encrypt 証明書取得時のエラー

Question

Let's Encrypt にて証明書を何度か発行しておりましたが、
突然エラーが発生し、証明書の発行が行えなくなりました。

以下のコマンドを実行

sudo ./letsencrypt-auto certonly --standalone -d xxx.com -d www.xxx.com

結果

Updating letsencrypt and virtual environment dependencies......
Requesting root privileges to run with virtualenv: /root/.local/share/letsencrypt/bin/letsencrypt certonly --standalone -d xxx.com -d www.xxx.com
An unexpected error occurred:
TypeError: coercing to Unicode: need string or buffer, NoneType found
Please see the logfiles in /var/log/letsencrypt for more details.

以下 /var/log/letsencrypt/letsencrypt.log

2015-12-29 15:54:33,970:DEBUG:letsencrypt.cli:Root logging level set at 30
2015-12-29 15:54:33,971:INFO:letsencrypt.cli:Saving debug log to /var/log/letsencrypt/letsencrypt.log
2015-12-29 15:54:33,971:DEBUG:letsencrypt.cli:letsencrypt version: 0.1.1
2015-12-29 15:54:33,971:DEBUG:letsencrypt.cli:Arguments: ['--standalone', '-d', 'xxx.com', '-d', 'www.xxx.com']
2015-12-29 15:54:33,972:DEBUG:letsencrypt.cli:Discovered plugins: PluginsRegistry(PluginEntryPoint#apache,PluginEntryPoint#webroot,PluginEntryPoint#null,PluginEntryPoint#manual,PluginEntryPoint#standalone)
2015-12-29 15:54:33,983:DEBUG:letsencrypt.cli:Requested authenticator standalone and installer None
2015-12-29 15:54:34,455:DEBUG:letsencrypt.display.ops:Single candidate plugin: * standalone
Description: Automatically use a temporary webserver
Interfaces: IAuthenticator, IPlugin
Entry point: standalone = letsencrypt.plugins.standalone:Authenticator
Initialized: <letsencrypt.plugins.standalone.Authenticator object at 0x37d08d0>
Prep: True
2015-12-29 15:54:34,455:DEBUG:letsencrypt.cli:Selected authenticator <letsencrypt.plugins.standalone.Authenticator object at 0x37d08d0> and installer None
2015-12-29 15:54:34,489:DEBUG:letsencrypt.cli:Picked account: <Account(b438c2205c083acf68a39547c3134fff)>
2015-12-29 15:54:34,490:DEBUG:root:Sending GET request to https://acme-v01.api.letsencrypt.org/directory. args: (), kwargs: {}
2015-12-29 15:54:34,500:INFO:requests.packages.urllib3.connectionpool:Starting new HTTPS connection (1): acme-v01.api.letsencrypt.org
2015-12-29 15:54:34,823:DEBUG:requests.packages.urllib3.connectionpool:"GET /directory HTTP/1.1" 200 263
2015-12-29 15:54:34,827:DEBUG:root:Received <Response [200]>. Headers: {'Content-Length': '263', 'Expires': 'Tue, 29 Dec 2015 15:54:34 GMT', 'Strict-Transport-Security': 'max-age=604800', 'Server': 'nginx', 'Connection': 'keep-alive', 'Pragma': 'no-cache', 'Cache-Control': 'max-age=0, no-cache, no-store', 'Date': 'Tue, 29 Dec 2015 15:54:34 GMT', 'X-Frame-Options': 'DENY', 'Content-Type': 'application/json', 'Replay-Nonce': 'RGvL6gWoJzpsSJJfKiT6C5Ar8cepzb43y5vMva1IupE'}. Content: '{"new-authz":"https://acme-v01.api.letsencrypt.org/acme/new-authz","new-cert":"https://acme-v01.api.letsencrypt.org/acme/new-cert","new-reg":"https://acme-v01.api.letsencrypt.org/acme/new-reg","revoke-cert":"https://acme-v01.api.letsencrypt.org/acme/revoke-cert"}'
2015-12-29 15:54:34,828:DEBUG:acme.client:Received response <Response [200]> (headers: {'Content-Length': '263', 'Expires': 'Tue, 29 Dec 2015 15:54:34 GMT', 'Strict-Transport-Security': 'max-age=604800', 'Server': 'nginx', 'Connection': 'keep-alive', 'Pragma': 'no-cache', 'Cache-Control': 'max-age=0, no-cache, no-store', 'Date': 'Tue, 29 Dec 2015 15:54:34 GMT', 'X-Frame-Options': 'DENY', 'Content-Type': 'application/json', 'Replay-Nonce': 'RGvL6gWoJzpsSJJfKiT6C5Ar8cepzb43y5vMva1IupE'}): '{"new-authz":"https://acme-v01.api.letsencrypt.org/acme/new-authz","new-cert":"https://acme-v01.api.letsencrypt.org/acme/new-cert","new-reg":"https://acme-v01.api.letsencrypt.org/acme/new-reg","revoke-cert":"https://acme-v01.api.letsencrypt.org/acme/revoke-cert"}'
2015-12-29 15:54:34,836:DEBUG:letsencrypt.storage:Expected symlink /etc/letsencrypt/live/xxx.com/cert.pem for cert does not exist.
2015-12-29 15:54:34,838:DEBUG:letsencrypt.cli:Exiting abnormally:
Traceback (most recent call last):
File "/root/.local/share/letsencrypt/bin/letsencrypt", line 11, in <module>
sys.exit(main())
File "/root/.local/share/letsencrypt/lib/python2.7/site-packages/letsencrypt/cli.py", line 1396, in main
return args.func(args, config, plugins)
File "/root/.local/share/letsencrypt/lib/python2.7/site-packages/letsencrypt/cli.py", line 598, in obtain_cert
_auth_from_domains(le_client, config, domains)
File "/root/.local/share/letsencrypt/lib/python2.7/site-packages/letsencrypt/cli.py", line 379, in _auth_from_domains
action, lineage = _treat_as_renewal(config, domains)
File "/root/.local/share/letsencrypt/lib/python2.7/site-packages/letsencrypt/cli.py", line 235, in _treat_as_renewal
ident_names_cert, subset_names_cert = _find_duplicative_certs(config, domains)
File "/root/.local/share/letsencrypt/lib/python2.7/site-packages/letsencrypt/cli.py", line 204, in _find_duplicative_certs
candidate_names = set(candidate_lineage.names())
File "/root/.local/share/letsencrypt/lib/python2.7/site-packages/letsencrypt/storage.py", line 459, in names
with open(target) as f:
TypeError: coercing to Unicode: need string or buffer, NoneType found

上記問題ご存知の方いらっしゃいませんでしょうか？
（実は英語にてそれっぽいソース発見しましたが、英語が分からず苦戦中です…）
Messing with /etc/letsencrypt leads to An unexpected error occurred. TypeError: coercing to Unicode: need string or buffer, NoneType found.

よろしくお願い致します。

Answer 1

どうやら、 /etc/letsencrypt/ ディレクトリを削除し、再度申請しなおせばこの問題が解決するようですが、
私の場合証明書を発行しすぎたせいで、制限に引っかかっているようです。
5証明書/7日との事ですので、7日後リトライしてみます。
ありがとうございました。