testsuite: Don't attempt to read .std{err,out} files if they don't exist

Simon reports that he was previously seeing framework failures due to
an attempt to read the non-existing T13456.stderr. While I don't know
exactly what this is due to, it does seem like a non-existing
.std{out,err} file should be equivalent to an empty file. Teach the
testsuite driver to treat it as such.

1 files changed, 10 insertions, 2 deletions

diff --git a/testsuite/driver/testlib.py b/testsuite/driver/testlib.py
index 535e31e110..abc01fdf95 100644
--- a/testsuite/driver/testlib.py
+++ b/testsuite/driver/testlib.py
@@ -1787,7 +1787,11 @@ def stdout_ok(name: TestName, way: WayName) -> bool:
                           expected_stdout_file, actual_stdout_file)
 
 def read_stdout( name: TestName ) -> str:
-    return in_testdir(name, 'run.stdout').read_text(encoding='UTF-8')
+    path = in_testdir(name, 'run.stdout')
+    if path.exists():
+        return path.read_text(encoding='UTF-8')
+    else:
+        return ''
 
 def dump_stdout( name: TestName ) -> None:
     s = read_stdout(name).strip()
@@ -1805,7 +1809,11 @@ def stderr_ok(name: TestName, way: WayName) -> bool:
                           whitespace_normaliser=normalise_whitespace)
 
 def read_stderr( name: TestName ) -> str:
-    return in_testdir(name, 'run.stderr').read_text(encoding='UTF-8')
+    path = in_testdir(name, 'run.stderr')
+    if path.exists():
+        return path.read_text(encoding='UTF-8')
+    else:
+        return ''
 
 def dump_stderr( name: TestName ) -> None:
     s = read_stderr(name).strip()