Sprinkle open(..., encoding=utf-8) (#48006)

Add missing encoding=utf-8 to various open calls. This makes
files like spec.json, spack.yaml, spack.lock, config.yaml etc locale
independent w.r.t. text encoding. In practice this is not often an
issue since Python 3.7, where the C locale is promoted to
C.UTF-8. But it's better to enforce UTF-8 explicitly, since there is
no guarantee text files are written in the right encoding.

Also avoid opening in text mode if it can be avoided.

share/spack/gitlab/cloud_pipelines/scripts/common/aggregate_package_logs.spack.py

@@ -32,7 +32,7 @@ def find_logs(prefix, filename):
     # Look in the CWD for logs
     local_log_path = os.path.join(os.getcwd(), args.log)
     if os.path.exists(local_log_path):
-        with open(local_log_path) as fd:
+        with open(local_log_path, encoding="utf-8") as fd:
             data.append(json.load(fd))
 
     # Look in the list of prefixes for logs
@@ -42,9 +42,9 @@ def find_logs(prefix, filename):
         print(f"  * found {len(logs)} logs")
         for log in logs:
             print(f"  * appending data for {log}")
-            with open(log) as fd:
+            with open(log, encoding="utf-8") as fd:
                 data.append(json.load(fd))
 
     print(f"Writing {args.output_file}")
-    with open(args.output_file, "w") as fd:
+    with open(args.output_file, "w", encoding="utf-8") as fd:
         json.dump(data, fd)