pipreqs online doesn't work behind proxy

Without "--use-local", I can't use pipreqs:

Error Traceback

```
>pipreqs
Traceback (most recent call last):
File "C:\Users\RUSANAN\AppData\Roaming\Python\Python39\site-packages\urllib3\connectionpool.py", line 700, in urlopen
self._prepare_proxy(conn)
File "C:\Users\RUSANAN\AppData\Roaming\Python\Python39\site-packages\urllib3\connectionpool.py", line 996, in _prepare_proxy
conn.connect()
File "C:\Users\RUSANAN\AppData\Roaming\Python\Python39\site-packages\urllib3\connection.py", line 414, in connect
self.sock = ssl_wrap_socket(
File "C:\Users\RUSANAN\AppData\Roaming\Python\Python39\site-packages\urllib3\util\ssl_.py", line 449, in ssl_wrap_socket
ssl_sock = _ssl_wrap_socket_impl(
File "C:\Users\RUSANAN\AppData\Roaming\Python\Python39\site-packages\urllib3\util\ssl_.py", line 493, in _ssl_wrap_socket_impl
return ssl_context.wrap_socket(sock, server_hostname=server_hostname)
File "c:\program files (x86)\python 3.9.6\lib\ssl.py", line 500, in wrap_socket
return self.sslsocket_class._create(
File "c:\program files (x86)\python 3.9.6\lib\ssl.py", line 1040, in _create
self.do_handshake()
File "c:\program files (x86)\python 3.9.6\lib\ssl.py", line 1309, in do_handshake
self._sslobj.do_handshake()
ssl.SSLCertVerificationError: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1129)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "C:\Users\RUSANAN\AppData\Roaming\Python\Python39\site-packages\requests\adapters.py", line 489, in send
resp = conn.urlopen(
File "C:\Users\RUSANAN\AppData\Roaming\Python\Python39\site-packages\urllib3\connectionpool.py", line 787, in urlopen
retries = retries.increment(
File "C:\Users\RUSANAN\AppData\Roaming\Python\Python39\site-packages\urllib3\util\retry.py", line 592, in increment
raise MaxRetryError(_pool, url, error or ResponseError(cause))
urllib3.exceptions.MaxRetryError: HTTPSConnectionPool(host='pypi.org', port=443): Max retries exceeded with url: /pypi/pyodbc/json (Caused by SSLError(SSLCertVerificationError(1, '[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1129)')))

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "c:\program files (x86)\python 3.9.6\lib\runpy.py", line 197, in _run_module_as_main
return _run_code(code, main_globals, None,
File "c:\program files (x86)\python 3.9.6\lib\runpy.py", line 87, in _run_code
exec(code, run_globals)
File "C:\Users\RUSANAN\AppData\Roaming\Python\Python39\Scripts\pipreqs.exe\__main__.py", line 7, in
File "C:\Users\RUSANAN\AppData\Roaming\Python\Python39\site-packages\pipreqs\pipreqs.py", line 488, in main
init(args)
File "C:\Users\RUSANAN\AppData\Roaming\Python\Python39\site-packages\pipreqs\pipreqs.py", line 439, in init
imports = local + get_imports_info(difference,
File "C:\Users\RUSANAN\AppData\Roaming\Python\Python39\site-packages\pipreqs\pipreqs.py", line 179, in get_imports_info
response = requests.get(
File "C:\Users\RUSANAN\AppData\Roaming\Python\Python39\site-packages\requests\api.py", line 73, in get
return request("get", url, params=params, **kwargs)
File "C:\Users\RUSANAN\AppData\Roaming\Python\Python39\site-packages\requests\api.py", line 59, in request
return session.request(method=method, url=url, **kwargs)
File "C:\Users\RUSANAN\AppData\Roaming\Python\Python39\site-packages\requests\sessions.py", line 587, in request
resp = self.send(prep, **send_kwargs)
File "C:\Users\RUSANAN\AppData\Roaming\Python\Python39\site-packages\requests\sessions.py", line 723, in send
history = [resp for resp in gen]
File "C:\Users\RUSANAN\AppData\Roaming\Python\Python39\site-packages\requests\sessions.py", line 723, in
history = [resp for resp in gen]
File "C:\Users\RUSANAN\AppData\Roaming\Python\Python39\site-packages\requests\sessions.py", line 266, in resolve_redirects
resp = self.send(
File "C:\Users\RUSANAN\AppData\Roaming\Python\Python39\site-packages\requests\sessions.py", line 701, in send
r = adapter.send(request, **kwargs)
File "C:\Users\RUSANAN\AppData\Roaming\Python\Python39\site-packages\requests\adapters.py", line 563, in send
raise SSLError(e, request=request)
requests.exceptions.SSLError: HTTPSConnectionPool(host='pypi.org', port=443): Max retries exceeded with url: /pypi/pyodbc/json (Caused by SSLError(SSLCertVerificationError(1, '[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1129)')))
```

I also have a pip.ini file configured with a index-url and trusted-host from my company:
pip.ini:
```
[global]
index-url = ...
trusted-host = ...
```

Start at pipreqs.py in get_imports_info, identified by the traceback around line 179, and trace how the online PyPI request is configured. Reproduce the command with the reported pip.ini proxy settings; done means pipreqs can perform the online lookup without the certificate or proxy failure.

Written by the indexing model from the issue text.