Fix encoding for files created for building package (issue python-poe…

…try#1027)

This is minimal set of modifications, which fixed the problem.

There are still more places, where files are open in text mode
without explicit encoding, thus possibly failing on systems not using
UTF-8 console encoding.

poetry/masonry/api.py

@@ -39,13 +39,13 @@ def prepare_metadata_for_build_wheel(metadata_directory, config_settings=None):
     dist_info.mkdir()
 
     if "scripts" in poetry.local_config or "plugins" in poetry.local_config:
-        with (dist_info / "entry_points.txt").open("w") as f:
+        with (dist_info / "entry_points.txt").open("w", encoding="utf-8") as f:
             builder._write_entry_points(f)
 
-    with (dist_info / "WHEEL").open("w") as f:
+    with (dist_info / "WHEEL").open("w", encoding="utf-8") as f:
         builder._write_wheel_file(f)
 
-    with (dist_info / "METADATA").open("w") as f:
+    with (dist_info / "METADATA").open("w", encoding="utf-8") as f:
         builder._write_metadata_file(f)
 
     return dist_info.name