undo workaround (#29)

* revert fix

It turns out python-tuf #2047 is not a bug after all, but rather a misconfiguration on the server-side:
The issue arises if the server sends a `Content-Encoding: gzip` header when it should *not* do so.

fixes #26

* clean up imports

src/tufup/client.py

@@ -8,11 +8,8 @@
 from urllib import parse
 
 import requests
-from requests.adapters import ReadTimeoutError
 from requests.auth import AuthBase
-from tuf.api.exceptions import (
-    DownloadError, SlowRetrievalError, UnsignedMetadataError
-)
+from tuf.api.exceptions import DownloadError, UnsignedMetadataError
 from tuf.api.metadata import TargetFile
 import tuf.ngclient
 # RequestsFetcher is "private", but we'll just have to live with that, for now.
@@ -345,23 +342,7 @@ def _get_session(self, url: str) -> requests.Session:
         return session
 
     def _chunks(self, response: "requests.Response") -> Iterator[bytes]:
-        """
-        Override _chunks() to:
-        - prevent automatic decoding of gzip files (python-tuf issue #2047)
-        - call progress hook
-
-        todo: adapt, if necessary, when a fix for python-tuf #2047 is released
-        """
-        try:
-            while True:
-                data = response.raw.read(
-                    amt=self.chunk_size, decode_content=False
-                )
-                if not data:
-                    break
-                self._progress(bytes_new=len(data))
-                yield data
-        except ReadTimeoutError as e:
-            raise SlowRetrievalError from e
-        finally:
-            response.close()
+        """Call progress hook for every chunk."""
+        for data in super()._chunks(response=response):
+            self._progress(bytes_new=len(data))
+            yield data

tests/test_client.py

@@ -278,11 +278,10 @@ def test__chunks_without_progress_hook(self):
         chunk_count = 10
         chunks = [b'x' * chunk_size] * chunk_count
 
-        def mock_read(**kwargs):
-            if chunks:
-                return chunks.pop()
+        def mock_iter_content(*args):
+            yield from chunks
 
-        mock_response = Mock(raw=Mock(read=mock_read), close=Mock())
+        mock_response = Mock(iter_content=mock_iter_content, close=Mock())
         fetcher = AuthRequestsFetcher()
         fetcher.chunk_size = chunk_size
         # _chunks should work even if attach_progress_hook was not called
@@ -297,11 +296,10 @@ def test__chunks_with_progress_hook(self):
         chunk_count = 10
         chunks = [b'x' * chunk_size] * chunk_count
 
-        def mock_read(**kwargs):
-            if chunks:
-                return chunks.pop()
+        def mock_iter_content(*args):
+            yield from chunks
 
-        mock_response = Mock(raw=Mock(read=mock_read), close=Mock())
+        mock_response = Mock(iter_content=mock_iter_content, close=Mock())
         fetcher = AuthRequestsFetcher()
         fetcher.chunk_size = chunk_size
         # test custom progress hook