SSL Issue: SSLError - bad handshake - certificate verify failed

Hello

Today I ran into a lot of ssl issues with my html5 notify platform and the coinmarketcap sensors, which are both throwing the same SSL band handshake error:

2018-05-08 09:20:29 ERROR (MainThread) [homeassistant.components.sensor] Error while setting up platform coinmarketcap
Traceback (most recent call last):
  File "/srv/homeassistant/lib/python3.5/site-packages/urllib3/contrib/pyopenssl.py", line 441, in wrap_socket
    cnx.do_handshake()
  File "/srv/homeassistant/lib/python3.5/site-packages/OpenSSL/SSL.py", line 1806, in do_handshake
    self._raise_ssl_error(self._ssl, result)
  File "/srv/homeassistant/lib/python3.5/site-packages/OpenSSL/SSL.py", line 1546, in _raise_ssl_error
    _raise_current_error()
  File "/srv/homeassistant/lib/python3.5/site-packages/OpenSSL/_util.py", line 54, in exception_from_error_queue
    raise exception_type(errors)
OpenSSL.SSL.Error: [('SSL routines', 'tls_process_server_certificate', 'certificate verify failed')]

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/srv/homeassistant/lib/python3.5/site-packages/urllib3/connectionpool.py", line 601, in urlopen
    chunked=chunked)
  File "/srv/homeassistant/lib/python3.5/site-packages/urllib3/connectionpool.py", line 346, in _make_request
    self._validate_conn(conn)
  File "/srv/homeassistant/lib/python3.5/site-packages/urllib3/connectionpool.py", line 850, in _validate_conn
    conn.connect()
  File "/srv/homeassistant/lib/python3.5/site-packages/urllib3/connection.py", line 326, in connect
    ssl_context=context)
  File "/srv/homeassistant/lib/python3.5/site-packages/urllib3/util/ssl_.py", line 329, in ssl_wrap_socket
    return context.wrap_socket(sock, server_hostname=server_hostname)
  File "/srv/homeassistant/lib/python3.5/site-packages/urllib3/contrib/pyopenssl.py", line 448, in wrap_socket
    raise ssl.SSLError('bad handshake: %r' % e)
ssl.SSLError: ("bad handshake: Error([('SSL routines', 'tls_process_server_certificate', 'certificate verify failed')],)",)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/srv/homeassistant/lib/python3.5/site-packages/requests/adapters.py", line 440, in send
    timeout=timeout
  File "/srv/homeassistant/lib/python3.5/site-packages/urllib3/connectionpool.py", line 639, in urlopen
    _stacktrace=sys.exc_info()[2])
  File "/srv/homeassistant/lib/python3.5/site-packages/urllib3/util/retry.py", line 388, in increment
    raise MaxRetryError(_pool, url, error or ResponseError(cause))
urllib3.exceptions.MaxRetryError: HTTPSConnectionPool(host='api.coinmarketcap.com', port=443): Max retries exceeded with url: /v1/ticker/iota/?convert=usd&limit=1 (Caused by SSLError(SSLError("bad handshake: Error([('SSL routines', 'tls_process_server_certificate', 'certificate verify failed')],)",),))

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/srv/homeassistant/lib/python3.5/site-packages/homeassistant/helpers/entity_platform.py", line 129, in _async_setup_platform
    SLOW_SETUP_MAX_WAIT, loop=hass.loop)
  File "/usr/lib/python3.5/asyncio/tasks.py", line 400, in wait_for
    return fut.result()
  File "/usr/lib/python3.5/asyncio/futures.py", line 293, in result
    raise self._exception
  File "/usr/lib/python3.5/concurrent/futures/thread.py", line 55, in run
    result = self.fn(*self.args, **self.kwargs)
  File "/srv/homeassistant/lib/python3.5/site-packages/homeassistant/components/sensor/coinmarketcap.py", line 56, in setup_platform
    CoinMarketCapData(currency, display_currency).update()
  File "/srv/homeassistant/lib/python3.5/site-packages/homeassistant/components/sensor/coinmarketcap.py", line 135, in update
    convert=self.display_currency)
  File "/srv/homeassistant/lib/python3.5/site-packages/coinmarketcap/core.py", line 82, in ticker
    response = self.__request('ticker/' + currency, params)
  File "/srv/homeassistant/lib/python3.5/site-packages/coinmarketcap/core.py", line 33, in __request
    response_object = self.session.get(self.base_url + endpoint, params = params, timeout = self.request_timeout)
  File "/srv/homeassistant/lib/python3.5/site-packages/requests/sessions.py", line 521, in get
    return self.request('GET', url, **kwargs)
  File "/srv/homeassistant/lib/python3.5/site-packages/requests_cache/core.py", line 126, in request
    **kwargs
  File "/srv/homeassistant/lib/python3.5/site-packages/requests/sessions.py", line 508, in request
    resp = self.send(prep, **send_kwargs)
  File "/srv/homeassistant/lib/python3.5/site-packages/requests_cache/core.py", line 99, in send
    return send_request_and_cache_response()
  File "/srv/homeassistant/lib/python3.5/site-packages/requests_cache/core.py", line 91, in send_request_and_cache_response
    response = super(CachedSession, self).send(request, **kwargs)
  File "/srv/homeassistant/lib/python3.5/site-packages/requests/sessions.py", line 618, in send
    r = adapter.send(request, **kwargs)
  File "/srv/homeassistant/lib/python3.5/site-packages/requests/adapters.py", line 506, in send
    raise SSLError(e, request=request)
requests.exceptions.SSLError: HTTPSConnectionPool(host='api.coinmarketcap.com', port=443): Max retries exceeded with url: /v1/ticker/iota/?convert=usd&limit=1 (Caused by SSLError(SSLError("bad handshake: Error([('SSL routines', 'tls_process_server_certificate', 'certificate verify failed')],)",),))

What could be the cause of this problem?ยจ

thank you in advance