regrtest: fix test to choose if header should be displayed (#3172)

Check "tests" before its value is replaced.

Lib/test/regrtest.py

@@ -572,6 +572,7 @@ def main(tests=None, testdir=None, verbose=0, quiet=False,
             nottests.add(arg)
         args = []
 
+    display_header = (verbose or header or not (quiet or single or tests or args)) and (not pgo)
     alltests = findtests(testdir, stdtests, nottests)
     selected = tests or args or alltests
     if single:
@@ -657,8 +658,7 @@ def main(tests=None, testdir=None, verbose=0, quiet=False,
         sys.stdout.flush()
 
     # For a partial run, we do not need to clutter the output.
-    if verbose or header or not (quiet or single or tests or args):
-        if not pgo:
+    if display_header:
         # Print basic platform information
         print "==", platform.python_implementation(), \
                     " ".join(sys.version.split())