requests: Fix detection of iterators in chunked data requests.

Chunked detection does not work as generators never have an `__iter__`
attribute.  They do have `__next__`.

Example that now works with this commit:

    def read_in_chunks(file_object, chunk_size=4096):
        while True:
            data = file_object.read(chunk_size)
            if not data:
                break
            yield data

    file = open(filename, "rb")
    r = requests.post(url, data=read_in_chunks(file))

python-ecosys/requests/manifest.py

@@ -1,3 +1,3 @@
-metadata(version="0.8.0", pypi="requests")
+metadata(version="0.8.1", pypi="requests")
 
 package("requests")

python-ecosys/requests/requests/__init__.py

@@ -45,7 +45,7 @@ def request(
     parse_headers=True,
 ):
     redirect = None  # redirection url, None means no redirection
-    chunked_data = data and getattr(data, "__iter__", None) and not getattr(data, "__len__", None)
+    chunked_data = data and getattr(data, "__next__", None) and not getattr(data, "__len__", None)
 
     if auth is not None:
         import ubinascii