gdb/testsuite: format some Python files

Format with black.

Change-Id: I28e79e9da07ea29391ad1942047633960fa72ed2
diff --git a/gdb/testsuite/gdb.python/py-pp-cast.py b/gdb/testsuite/gdb.python/py-pp-cast.py
index a0c48f9..c071920 100644
--- a/gdb/testsuite/gdb.python/py-pp-cast.py
+++ b/gdb/testsuite/gdb.python/py-pp-cast.py
@@ -15,6 +15,7 @@
 
 import gdb.printing
 
+
 class PpIntPrinter(object):
     def __init__(self, val):
         self.val = val
diff --git a/gdb/testsuite/gdb.python/py-pp-re-notag.py b/gdb/testsuite/gdb.python/py-pp-re-notag.py
index 3bbf588..00bc5c7 100644
--- a/gdb/testsuite/gdb.python/py-pp-re-notag.py
+++ b/gdb/testsuite/gdb.python/py-pp-re-notag.py
@@ -18,6 +18,7 @@
 import gdb  # silence pyflakes
 import gdb.printing
 
+
 class TimePrinter:
     def __init__(self, val):
         self.val = val
diff --git a/gdb/testsuite/gdb.python/py-prettyprint-stub.py b/gdb/testsuite/gdb.python/py-prettyprint-stub.py
index 75d5f35..2378f55 100644
--- a/gdb/testsuite/gdb.python/py-prettyprint-stub.py
+++ b/gdb/testsuite/gdb.python/py-prettyprint-stub.py
@@ -18,6 +18,7 @@
 
 import gdb.printing
 
+
 class SPrinter:
     def __init__(self, val):
         self.val = val