[Lint] Use Black to auto-format code

The move to using auto-formatter makes it easier to read, submit and
speeds up development time. https://github.com/ambv/black/

Although I would prefer 79 chars, the default line length of 88 chars
used by black suffices. The flake8 line length remains at 120 chars
since black does not touch comments or docstrings and this will require
another round of fixes.

The only black setting that is not standard is the use of double-quotes
for strings so disabled any formatting of these. Note however that
flake8 will still flag usage of double-quotes. I may change my mind on
double vs single quotes but for now leave them.

A new pyproject.toml file has been created for black configuration.

minify_web_js.py

@@ -35,13 +35,25 @@ def module_exists(module_name):
 
 # Imports sorted by resulting file size.
 if module_exists('closure'):
+
     def minify_closure(file_in, file_out):
         try:
-            subprocess.check_call(['closure', '-W', 'QUIET',
-                                   '--js', file_in, '--js_output_file', file_out])
+            subprocess.check_call(
+                [
+                    'closure',
+                    '-W',
+                    'QUIET',
+                    '--js',
+                    file_in,
+                    '--js_output_file',
+                    file_out,
+                ]
+            )
             return True
         except subprocess.CalledProcessError:
             return False
+
+
 elif module_exists('slimit'):
     from slimit import minify
 else:
@@ -108,7 +120,10 @@ def minify_js_dir(source_dir):
 
 if __name__ == '__main__':
     if len(sys.argv) != 2:
-        JS_SOURCE_DIRS = ['deluge/ui/web/js/deluge-all', 'deluge/ui/web/js/extjs/ext-extensions']
+        JS_SOURCE_DIRS = [
+            'deluge/ui/web/js/deluge-all',
+            'deluge/ui/web/js/extjs/ext-extensions',
+        ]
     else:
         JS_SOURCE_DIRS = [os.path.abspath(sys.argv[1])]