Don't raise exceptions when offline #751
Description
When I am offline pydoctor is of course not able to retrieve intersphinx files.
Currently this does raise an exception. This should not happen. Just print an error.
ERROR - Could not retrieve intersphinx object.inv from https://python-docx.readthedocs.io/en/stable/objects.inv
Traceback (most recent call last):
File "C:\python\Lib\site-packages\urllib3\connection.py", line 174, in _new_conn
conn = connection.create_connection(
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\python\Lib\site-packages\urllib3\util\connection.py", line 72, in create_connection
for res in socket.getaddrinfo(host, port, family, socket.SOCK_STREAM):
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\python\Lib\socket.py", line 962, in getaddrinfo
for res in _socket.getaddrinfo(host, port, family, type, proto, flags):
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
socket.gaierror: [Errno 11001] getaddrinfo failed
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "C:\python\Lib\site-packages\urllib3\connectionpool.py", line 714, in urlopen
httplib_response = self._make_request(
^^^^^^^^^^^^^^^^^^^
File "C:\python\Lib\site-packages\urllib3\connectionpool.py", line 403, in _make_request
self._validate_conn(conn)
File "C:\python\Lib\site-packages\urllib3\connectionpool.py", line 1053, in _validate_conn
conn.connect()
File "C:\python\Lib\site-packages\urllib3\connection.py", line 363, in connect
self.sock = conn = self._new_conn()
^^^^^^^^^^^^^^^^
File "C:\python\Lib\site-packages\urllib3\connection.py", line 186, in _new_conn
raise NewConnectionError(
urllib3.exceptions.NewConnectionError: <urllib3.connection.HTTPSConnection object at 0x0000024AC15F0510>: Failed to establish a new connection: [Errno 11001] getaddrinfo failed