fill out bz2 stub (#1728)

- add a default value to ...
- add some missing version checks
- add some missing arguments

stdlib/2and3/bz2.pyi

@@ -1,20 +1,29 @@
-# Stubs for bz2
+import sys
+from typing import Any, BinaryIO, IO, Optional, Union
 
-from typing import Any, BinaryIO, TextIO, IO, Optional, Union
+if sys.version_info >= (3, 6):
+    from os import PathLike
+    _PathOrFile = Union[str, bytes, IO[Any], PathLike[Any]]
+elif sys.version_info >= (3, 3):
+    _PathOrFile = Union[str, bytes, IO[Any]]
+else:
+    _PathOrFile = str
 
 def compress(data: bytes, compresslevel: int = ...) -> bytes: ...
 def decompress(data: bytes) -> bytes: ...
 
-def open(filename: Union[str, bytes, IO[Any]],
-         mode: str = ...,
-         encoding: Optional[str] = ...,
-         errors: Optional[str] = ...,
-         newline: Optional[str] = ...) -> IO[Any]: ...
+if sys.version_info >= (3, 3):
+    def open(filename: _PathOrFile,
+             mode: str = ...,
+             compresslevel: int = ...,
+             encoding: Optional[str] = ...,
+             errors: Optional[str] = ...,
+             newline: Optional[str] = ...) -> IO[Any]: ...
 
 class BZ2File(BinaryIO):
     def __init__(self,
-                 filename: Union[str, bytes, IO[Any]],
-                 mode: str = "r",
+                 filename: _PathOrFile,
+                 mode: str = ...,
                  buffering: Optional[Any] = ...,
                  compresslevel: int = ...) -> None: ...
 
@@ -24,10 +33,15 @@ class BZ2Compressor(object):
     def flush(self) -> bytes: ...
 
 class BZ2Decompressor(object):
-    def decompress(self, data: bytes) -> bytes: ...
-    @property
-    def eof(self) -> bool: ...
-    @property
-    def needs_input(self) -> bool: ...
+    if sys.version_info >= (3, 5):
+        def decompress(self, data: bytes, max_length: int = ...) -> bytes: ...
+    else:
+        def decompress(self, data: bytes) -> bytes: ...
+    if sys.version_info >= (3, 3):
+        @property
+        def eof(self) -> bool: ...
+    if sys.version_info >= (3, 5):
+        @property
+        def needs_input(self) -> bool: ...
     @property
     def unused_data(self) -> bytes: ...