Correct print() calls to print a blank line in various test cases

Lib/test/test_curses.py

@@ -63,7 +63,7 @@ class TestCurses(unittest.TestCase):
     def setUp(self):
         if verbose:
             # just to make the test output a little more readable
-            print()
+            print('')
         self.stdscr = curses.initscr()
         curses.savetty()
 

Lib/test/test_httpservers.py

@@ -442,7 +442,7 @@ cgi_file4 = """\
 import os
 
 print("Content-type: text/html")
-print()
+print("")
 
 print(os.environ["%s"])
 """

Lib/test/test_subprocess.py

@@ -426,7 +426,7 @@ class ProcessTestCase(BaseTestCase):
     def test_communicate_pipe_fd_leak(self):
         fd_directory = '/proc/%d/fd' % os.getpid()
         num_fds_before_popen = len(os.listdir(fd_directory))
-        p = subprocess.Popen([sys.executable, "-c", "print()"],
+        p = subprocess.Popen([sys.executable, "-c", "print('')"],
                              stdout=subprocess.PIPE)
         p.communicate()
         num_fds_after_communicate = len(os.listdir(fd_directory))