Fix arg types for os.execv* (#1075)

Author: euresti

stdlib/2/os/__init__.pyi

@@ -201,10 +201,15 @@ def execl(file: _PathType, *args) -> None: ...
 def execle(file: _PathType, *args) -> None: ...
 def execlp(file: _PathType, *args) -> None: ...
 def execlpe(file: _PathType, *args) -> None: ...
-def execv(path: _PathType, args: Union[Tuple[Union[bytes, Text]], List[Union[bytes, Text]]]) -> None: ...
-def execve(path: _PathType, args: Union[Tuple[Union[bytes, Text]], List[Union[bytes, Text]]], env: Mapping[str, str]) -> None: ...
-def execvp(file: _PathType, args: Union[Tuple[Union[bytes, Text]], List[Union[bytes, Text]]]) -> None: ...
-def execvpe(file: _PathType, args: Union[Tuple[Union[bytes, Text]], List[Union[bytes, Text]]], env: Mapping[str, str]) -> None: ...
+
+# The docs say `args: tuple or list of strings`
+# The implementation enforces tuple or list so we can't use Sequence.
+_ExecVArgs = Union[Tuple[Union[bytes, Text], ...], List[bytes], List[Text], List[Union[bytes, Text]]]
+def execv(path: _PathType, args: _ExecVArgs) -> None: ...
+def execve(path: _PathType, args: _ExecVArgs, env: Mapping[str, str]) -> None: ...
+def execvp(file: _PathType, args: _ExecVArgs) -> None: ...
+def execvpe(file: _PathType, args: _ExecVArgs, env: Mapping[str, str]) -> None: ...
+
 def _exit(n: int) -> NoReturn: ...
 def fork() -> int: ...
 def forkpty() -> Tuple[int, int]: ...

stdlib/3/os/__init__.pyi

@@ -346,10 +346,15 @@ def execle(path: _PathType, arg0: Union[bytes, Text],
 def execlp(path: _PathType, arg0: Union[bytes, Text], *args: Union[bytes, Text]) -> None: ...
 def execlpe(path: _PathType, arg0: Union[bytes, Text],
             *args: Any) -> None: ...  # Imprecise signature
-def execv(path: _PathType, args: Union[Tuple[Union[bytes, Text]], List[Union[bytes, Text]]]) -> None: ...
-def execve(path: _PathType, args: Union[Tuple[Union[bytes, Text]], List[Union[bytes, Text]]], env: Mapping[str, str]) -> None: ...
-def execvp(file: _PathType, args: Union[Tuple[Union[bytes, Text]], List[Union[bytes, Text]]]) -> None: ...
-def execvpe(file: _PathType, args: Union[Tuple[Union[bytes, Text]], List[Union[bytes, Text]]], env: Mapping[str, str]) -> None: ...
+
+# The docs say `args: tuple or list of strings`
+# The implementation enforces tuple or list so we can't use Sequence.
+_ExecVArgs = Union[Tuple[Union[bytes, Text], ...], List[bytes], List[Text], List[Union[bytes, Text]]]
+def execv(path: _PathType, args: _ExecVArgs) -> None: ...
+def execve(path: _PathType, args: _ExecVArgs, env: Mapping[str, str]) -> None: ...
+def execvp(file: _PathType, args: _ExecVArgs) -> None: ...
+def execvpe(file: _PathType, args: _ExecVArgs, env: Mapping[str, str]) -> None: ...
+
 def _exit(n: int) -> NoReturn: ...
 def fork() -> int: ...  # Unix only
 def forkpty() -> Tuple[int, int]: ...  # some flavors of Unix