Fix downloading packages from Simplepypi (#1851)

* fix downloading packages from simplepypi

* unused code removed

* remove unused imports

poetry/utils/inspector.py

@@ -3,8 +3,6 @@
 import tarfile
 import zipfile
 
-from bz2 import BZ2File
-from gzip import GzipFile
 from typing import Dict
 from typing import List
 from typing import Union
@@ -114,27 +112,21 @@ def inspect_sdist(
         # Still not dependencies found
         # So, we unpack and introspect
         suffix = file_path.suffix
-        gz = None
         if suffix == ".zip":
             tar = zipfile.ZipFile(str(file_path))
         else:
             if suffix == ".bz2":
-                gz = BZ2File(str(file_path))
                 suffixes = file_path.suffixes
                 if len(suffixes) > 1 and suffixes[-2] == ".tar":
                     suffix = ".tar.bz2"
             else:
-                gz = GzipFile(str(file_path))
                 suffix = ".tar.gz"
 
-            tar = tarfile.TarFile(str(file_path), fileobj=gz)
+            tar = tarfile.open(str(file_path))
 
         try:
             tar.extractall(os.path.join(str(file_path.parent), "unpacked"))
         finally:
-            if gz:
-                gz.close()
-
             tar.close()
 
         unpacked = file_path.parent / "unpacked"