proxy: fix parser in non-authorization-case

[yamahubuki]

I fixed the bug in parsing proxyInfo from environment.

When describing a proxy address, it is common not to write a scheme like 'https: //'.

However, urllib.parse.urlparse is not handling the description without the scheme correctly.

>>> import sys
>>> sys.version
'3.8.5 (tags/v3.8.5:580fbb0, Jul 20 2020, 15:43:08) [MSC v.1926 32 bit (Intel)]'

>>> import urllib
>>> import urllib.parse
>>> urllib.parse.urlparse("http://id:pw@example.com:8080")
ParseResult(scheme='http', netloc='id:pw@example.com:8080', path='', params='', query='', fragment='')
>>> urllib.parse.urlparse("http://example.com:8080")
ParseResult(scheme='http', netloc='example.com:8080', path='', params='', query='', fragment='')

I was having trouble connecting to the proxy, so I rewrote it to code that doesn't use urllib.

[temoto]

@yamahubuki do you want to write a test?

[yamahubuki]

@temoto
I added the testcase and fix code for pass existing cases.

[temoto]

@yamahubuki please rebase on master, it has CI fixed, it should show test failure in py2.

[yamahubuki]

@temoto
I merged latest master.
But I cannot view the test result from workflow.

The displayed message is as follows.

3 workflows awaiting approval
First-time contributors need a maintainer to approve running workflows

Would you allow me the workflow to run?

[temoto]

IMHO, best option here is detect have:colon@without.double// then add default scheme in front and make urlparse great again.