Auto-format Python files with black

This patch is strictly the result of:
$ black $(git ls-files '*.py')

There have been no manual changes.

bin/tests/system/inline/tests_signed_zone_files.py

@@ -14,29 +14,29 @@ import struct
 
 
 class RawFormatHeader(dict):
-    '''
+    """
     A dictionary of raw-format header fields read from a zone file.
-    '''
+    """
 
     fields = [
-        'format',
-        'version',
-        'dumptime',
-        'flags',
-        'sourceserial',
-        'lastxfrin',
+        "format",
+        "version",
+        "dumptime",
+        "flags",
+        "sourceserial",
+        "lastxfrin",
     ]
 
     def __init__(self, file_name):
-        header = struct.Struct('>IIIIII')
-        with open(file_name, 'rb') as data:
+        header = struct.Struct(">IIIIII")
+        with open(file_name, "rb") as data:
             header_data = data.read(header.size)
         super().__init__(zip(self.fields, header.unpack_from(header_data)))
 
 
 def test_unsigned_serial_number():
 
-    '''
+    """
     Check whether all signed zone files in the "ns8" subdirectory contain the
     serial number of the unsigned version of the zone in the raw-format header.
     The test assumes that all "*.signed" files in the "ns8" subdirectory are in
@@ -51,18 +51,18 @@ def test_unsigned_serial_number():
 
       - example[0-9][0-9].com.db.signed files are initially signed by
         dnssec-signzone while the others - by named.
-    '''
+    """
 
     zones_with_unsigned_serial_missing = []
 
-    for signed_zone in sorted(glob.glob('ns8/*.signed')):
+    for signed_zone in sorted(glob.glob("ns8/*.signed")):
         raw_header = RawFormatHeader(signed_zone)
         # Ensure the unsigned serial number is placed where it is expected.
-        assert raw_header['format'] == 2
-        assert raw_header['version'] == 1
+        assert raw_header["format"] == 2
+        assert raw_header["version"] == 1
         # Check whether the header flags indicate that the unsigned serial
         # number is set and that the latter is indeed set.
-        if raw_header['flags'] & 0x02 == 0 or raw_header['sourceserial'] == 0:
+        if raw_header["flags"] & 0x02 == 0 or raw_header["sourceserial"] == 0:
             zones_with_unsigned_serial_missing.append(signed_zone)
 
     assert not zones_with_unsigned_serial_missing