Keep memory report aligned in regrtest output (#159967)

Author: zware

Lib/test/libregrtest/logger.py

@@ -29,11 +29,12 @@ def log(self, line: str = '') -> None:
         if self.get_mem_usage is not None:
             mem = self.get_mem_usage()
             if mem:
-                mib = mem / (1024*1024)
-                if mib >= 1024:
-                    line = f"mem: {mib / 1024:.1f} GiB {line}"
-                else:
-                    line = f"mem: {mib:.1f} MiB {line}"
+                qty = mem / (1024*1024)
+                unit = 'MiB'
+                if qty >= 1024:
+                    qty = qty / 1024
+                    unit = 'GiB'
+                line = f"mem: {qty:6.1f} {unit} {line}"
 
         # Add the system load prefix: "load avg: 1.80 "
         load_avg = self.get_load_avg()

Lib/test/test_regrtest.py

@@ -48,7 +48,7 @@
 LOG_PREFIX = (
     r'[0-9]+:[0-9]+:[0-9]+ '
     r'(?:load avg: [0-9]+\.[0-9]{2} )?'
-    r'(?:mem: [0-9]+\.[0-9] (?:MiB|GiB) )?'
+    r'(?:mem: +[0-9]+\.[0-9] (?:MiB|GiB) )?'
 )
 RESULT_REGEX = (
     'passed',