The ijg server seems to have a web crawler protection that blocks all requests without the User-Agent header.
This pull request fixes this problem.
```
PS D:\Projects\python_c\Pillow-master\winbuild> python build_dep.py
Fetching http://www.ijg.org/files/jpegsr9c.zip
Traceback (most recent call last):
File "D:\Projects\python_c\Pillow-master\winbuild\fetch.py", line 13, in fetch
r = urllib.request.urlopen(url)
File "C:\Users\W0lf\AppData\Local\Programs\Python\Python37\lib\urllib\request.py", line 222, in urlopen
return opener.open(url, data, timeout)
File "C:\Users\W0lf\AppData\Local\Programs\Python\Python37\lib\urllib\request.py", line 531, in open
response = meth(req, response)
File "C:\Users\W0lf\AppData\Local\Programs\Python\Python37\lib\urllib\request.py", line 641, in http_response
'http', request, response, code, msg, hdrs)
File "C:\Users\W0lf\AppData\Local\Programs\Python\Python37\lib\urllib\request.py", line 569, in error
return self._call_chain(*args)
File "C:\Users\W0lf\AppData\Local\Programs\Python\Python37\lib\urllib\request.py", line 503, in _call_chain
result = func(*args)
File "C:\Users\W0lf\AppData\Local\Programs\Python\Python37\lib\urllib\request.py", line 649, in http_error_default
raise HTTPError(req.full_url, code, msg, hdrs, fp)
urllib.error.HTTPError: HTTP Error 403: Forbidden
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "build_dep.py", line 343, in <module>
extract_libs()
File "build_dep.py", line 50, in extract_libs
filename = fetch(lib["url"])
File "D:\Projects\python_c\Pillow-master\winbuild\fetch.py", line 15, in fetch
r = urllib.request.urlopen(url)
File "C:\Users\W0lf\AppData\Local\Programs\Python\Python37\lib\urllib\request.py", line 222, in urlopen
return opener.open(url, data, timeout)
File "C:\Users\W0lf\AppData\Local\Programs\Python\Python37\lib\urllib\request.py", line 531, in open
response = meth(req, response)
File "C:\Users\W0lf\AppData\Local\Programs\Python\Python37\lib\urllib\request.py", line 641, in http_response
'http', request, response, code, msg, hdrs)
File "C:\Users\W0lf\AppData\Local\Programs\Python\Python37\lib\urllib\request.py", line 569, in error
return self._call_chain(*args)
File "C:\Users\W0lf\AppData\Local\Programs\Python\Python37\lib\urllib\request.py", line 503, in _call_chain
result = func(*args)
File "C:\Users\W0lf\AppData\Local\Programs\Python\Python37\lib\urllib\request.py", line 649, in http_error_default
raise HTTPError(req.full_url, code, msg, hdrs, fp)
urllib.error.HTTPError: HTTP Error 403: Forbidden
```
This better follows PEP 8 style guide:
https://www.python.org/dev/peps/pep-0008/#imports
> Imports are always put at the top of the file, just after any module
> comments and docstrings, and before module globals and constants.
This also avoids duplicate import code within the same file.
