respect no_proxy environment variable and proxies['no'] parameter

#!/usr/bin/python2

# license = public domain

import os
import random
import time
import requests
import BaseHTTPServer
import thread
import bs4

tor_host = '127.0.0.1'
#tor_port = 9050 # system-wide tor
tor_port = 9150 # torbrowser tor

# do not use tor to connect to local or private hosts
# see https://en.wikipedia.org/wiki/Reserved_IP_addresses
no_proxy_list = [
        # hostnames are not resolved locally with socks5h proxy
        'localhost',
        'localhost.localdomain',
        # IPv4
        '127.0.0.0/8', # localhost
        # subnets
        '169.254.0.0/16',
        '255.255.255.255',
        # LAN aka private networks
        '10.0.0.0/8',
        '100.64.0.0/10',
        '172.16.0.0/12',
        '192.0.0.0/24',
        '192.168.0.0/16',
        '198.18.0.0/15',
        # IPv6
        '::1/128', # localhost
        'fc00::/7', # LAN
        'fe80::/10', # link-local
]

# variant 1
os.environ['no_proxy'] = ','.join(no_proxy_list)

def get_tor_session(tor_host='127.0.0.1', tor_port=9050,
        torbrowser_headers=[], no_proxy_list=[]):

        session = requests.session()

        # variant 1
        session.trust_env = True
        #session.trust_env = False # ignore environment variables

        # socks5h scheme = remote DNS = no DNS leaks
        p = 'socks5h://{0}:{1}'.format(tor_host, tor_port)
        session.proxies = {
                'http' : p,
                'https': p,

                # variant 2
                'no': ','.join(no_proxy_list)
        }

        if torbrowser_headers == []:
                print('warning. got no torbrowser_headers')
                # at least imitate torbrowser from year 2018
                torbrowser_headers = [
                        ('accept-language', 'en-US,en;q=0.5'),
                        ('accept', 'text/html,application/xhtml+xml,' \
                                + 'application/xml;q=0.9,*/*;q=0.8'),
                        ('user-agent', 'Mozilla/5.0 (Windows NT 6.1; rv:60.0) ' \
                                + 'Gecko/20100101 Firefox/60.0'),
                        ('upgrade-insecure-requests', '1'),
                ]

        for k, v in torbrowser_headers:
                # header 'host' is dynamic
                # header 'connection' = 'keep-alive' is set internally
                if k not in ['host', 'connection']:
                        session.headers[k] = v

        return session



tor = get_tor_session(tor_host, tor_port, [], no_proxy_list)



test_host = '127.0.0.1'
test_port = random.randint(8000, 16000)
test_url = 'http://{0}:{1}/'.format(test_host, test_port)

def test_tor_get(test_url):
        time.sleep(2) # wait for http server to start
        tor.get(test_url)
thread.start_new_thread(test_tor_get, (test_url,))

test_headers = [] # global
class test_handler(BaseHTTPServer.BaseHTTPRequestHandler):
        def do_GET(self): # handle GET request
                global test_headers
                test_headers = self.headers.items()
                self.send_response(204, 'No Content')
                self.end_headers()

serv = BaseHTTPServer.HTTPServer((test_host, test_port), test_handler)
serv.handle_request() # handle one request
del serv

print('tor.get headers')
for k, v in test_headers:
        print('header %s: %s' % (k, v))

#print('tor ip '+tor.get("http://httpbin.org/ip").text)

print('tor check ' + \
bs4.BeautifulSoup(
tor.get("https://check.torproject.org/").text, 'html.parser'
).title.string.strip())

--- a/utils.py
+++ b/utils.py
@@ -757,7 +757,7 @@
     :rtype: dict
     """
     if should_bypass_proxies(url, no_proxy=no_proxy):
-        return {}
+        return {'__bypass_proxies': True}
     else:
         return getproxies()


--- a/sessions.py
+++ b/sessions.py
@@ -698,8 +698,15 @@
                 verify = (os.environ.get('REQUESTS_CA_BUNDLE') or
                           os.environ.get('CURL_CA_BUNDLE'))

+        if 'no' in self.proxies:
+            if should_bypass_proxies(url, no_proxy=self.proxies['no']):
+                proxies = {'__bypass_proxies': True}
+
         # Merge all the kwargs.
-        proxies = merge_setting(proxies, self.proxies)
+        if '__bypass_proxies' in proxies:
+            proxies = {} # bypass proxies for this request
+        else:
+            proxies = merge_setting(proxies, self.proxies)
         stream = merge_setting(stream, self.stream)
         verify = merge_setting(verify, self.verify)
         cert = merge_setting(cert, self.cert)