Make _open_gz piped program opening simpler

Author: rhpvorderman

src/xopen/__init__.py

@@ -492,9 +492,7 @@ def _open_zst(  # noqa: C901
     return f
 
 
-def _open_gz(  # noqa: C901
-    filename, mode: str, compresslevel, threads, **text_mode_kwargs
-):
+def _open_gz(filename, mode: str, compresslevel, threads, **text_mode_kwargs):
     assert "b" in mode
     if compresslevel is None:
         # Force the same compression level on every tool regardless of
@@ -523,18 +521,14 @@ def _open_gz(  # noqa: C901
                 )
             except zlib_ng.error:  # Bad compression level
                 pass
+
+    for program in ("pigz", "gzip"):
         try:
-            try:
-                return _PipedCompressionProgram(
-                    filename, mode, compresslevel, threads, **_program_settings("pigz")
-                )
-            except OSError:
-                return _PipedCompressionProgram(
-                    filename, mode, compresslevel, threads, **_program_settings("gzip")
-                )
+            return _PipedCompressionProgram(
+                filename, mode, compresslevel, threads, **_program_settings(program)
+            )
         except OSError:
-            pass  # We try without threads.
-
+            pass
     return _open_reproducible_gzip(
         filename,
         mode=mode,