test/infamy: make until() exception-safe

Any exception raised by fn() propagated immediately out of the retry
loop, effectively making until() a single-shot call the moment any
transient error occurred.

Fix by wrapping fn() in a try/except inside the loop and treating any
exception as a "not yet" result.  The last exception is preserved and
re-raised if all attempts are exhausted, so failure output is still
meaningful.  Also fix a missing newline at end of file.

Fixes #1403

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

test/infamy/util.py

@@ -38,13 +38,20 @@ def parallel(*fns):
 
 
 def until(fn, attempts=10, interval=1):
+    last_exc = None
     for attempt in range(attempts):
-        result = fn()
+        try:
+            result = fn()
+        except Exception as e:
+            last_exc = e
+            result = False
         if result:
             return result
 
         time.sleep(interval)
 
+    if last_exc:
+        raise last_exc
     raise Exception("Expected condition did not materialize")
 
 
@@ -119,4 +126,4 @@ def curl(url, timeout=10, silent=False):
     except (urllib.error.URLError, ConnectionResetError, UnicodeEncodeError, TimeoutError) as e:
         if not silent:
             print(f"[WARN] curl: failed to fetch {url}: {e}")
-        return ""
+        return ""