requests: Requests 2.11: check_header_validity failed on header with integer value

Hi,

Since requests 2.11, all my calls using requests for my app are broken. After debugging, it seems that this version does not accept header with integer value, like it was before.

2.10:

In [1]: import requests

In [2]: requests.get('http://bing.com', headers={'Content-Length': 42})
Out[2]: <Response [200]>

2.11

In [1]: import requests

In [2]: requests.get('http://bing.com', headers={'Content-Length': 42})
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
D:\VSProjects\azure-sdk-for-python\env3.5\Lib\site-packages\requests\utils.py in check_header_validity(header)
    751     try:
--> 752         if not pat.match(value):
    753             raise InvalidHeader("Invalid return character or leading space in header: %s" % name)

TypeError: expected string or bytes-like object

During handling of the above exception, another exception occurred:

InvalidHeader                             Traceback (most recent call last)
<ipython-input-2-ae7ec2933e34> in <module>()
----> 1 requests.get('http://bing.com', headers={'Content-Length': 42})

D:\VSProjects\azure-sdk-for-python\env3.5\Lib\site-packages\requests\api.py in get(url, params, **kwargs)
     68
     69     kwargs.setdefault('allow_redirects', True)
---> 70     return request('get', url, params=params, **kwargs)
     71
     72

D:\VSProjects\azure-sdk-for-python\env3.5\Lib\site-packages\requests\api.py in request(method, url, **kwargs)
     54     # cases, and look like a memory leak in others.
     55     with sessions.Session() as session:
---> 56         return session.request(method=method, url=url, **kwargs)
     57
     58

D:\VSProjects\azure-sdk-for-python\env3.5\Lib\site-packages\requests\sessions.py in request(self, method, url, params, data, headers, cookies, files, auth, timeout, allow_redirects, proxies, hooks, stream, verify, cert, json)
    455             hooks = hooks,
    456         )
--> 457         prep = self.prepare_request(req)
    458
    459         proxies = proxies or {}

D:\VSProjects\azure-sdk-for-python\env3.5\Lib\site-packages\requests\sessions.py in prepare_request(self, request)
    388             auth=merge_setting(auth, self.auth),
    389             cookies=merged_cookies,
--> 390             hooks=merge_hooks(request.hooks, self.hooks),
    391         )
    392         return p

D:\VSProjects\azure-sdk-for-python\env3.5\Lib\site-packages\requests\models.py in prepare(self, method, url, headers, files, data, params, auth, cookies, hooks, json)
    293         self.prepare_method(method)
    294         self.prepare_url(url, params)
--> 295         self.prepare_headers(headers)
    296         self.prepare_cookies(cookies)
    297         self.prepare_body(data, files, json)

D:\VSProjects\azure-sdk-for-python\env3.5\Lib\site-packages\requests\models.py in prepare_headers(self, headers)
    407             for header in headers.items():
    408                 # Raise exception on invalid header value.
--> 409                 check_header_validity(header)
    410                 name, value = header
    411                 self.headers[to_native_string(name)] = value

D:\VSProjects\azure-sdk-for-python\env3.5\Lib\site-packages\requests\utils.py in check_header_validity(header)
    754     except TypeError:
    755         raise InvalidHeader("Header value %s must be of type str or bytes, "
--> 756                             "not %s" % (value, type(value)))
    757
    758

InvalidHeader: Header value 42 must be of type str or bytes, not <class 'int'>

We define ‘Content-Length’ in each request. Anyway, using an integer for an header which is semantically an integer makes sense no?