Incorrect Space Added after Assignment Expression in If Statement

[t-mart]

Description
Black on the current master@c53853f and (19.10b0) adds a space after Assignment Expressions and before the final colon in if statements.

For what it's worth, I'm not sure if this is actually intended behavior or not, but it doesn't seem like it. No other parenthesized expressions in if statements get this treatment.

To Reproduce:

1. Put this example in a file:

   if (foo := True):
       print(foo)

2. Run black <file> --diff

Expected behavior
Black should not need to act upon this file. There should be no diff output and black should claim 1 file would be left unchanged.

Actual behavior
Black currently inserts a space between the end of the assignment expression and the colon.

Actual black <file> --diff output:

--- blacktest.py        2019-11-23 00:56:09.070688 +0000
+++ blacktest.py        2019-11-23 00:56:15.282759 +0000
@@ -1,3 +1,3 @@
-if (foo := True):
+if (foo := True) :
     print(foo)

Environment:

• Version: current master@c53853f
  
• OS and Python version: Windows 10 and Linux tested with Python 3.8.0

Does this bug also happen on master?
Yes

Other Information
This also affects if statements that are broken up into several lines.

The following example comes come a current project, excuse the specificity. The # pylint: disable=superfluous-parens should be treated simply as a comment for the scope of this issue. (In reality, pylint is also currently having a problem with assignment expressions)

class Foo:
    def method(self):
        if (
            invalid_reasons := self.invalid_reasons()
        ):  # pylint: disable=superfluous-parens
            LOGGER.error(
                f"Not saving raid for the following reasons: {', '.join(invalid_reasons)}"
            )
            return

--- blacktest.py        2019-11-23 01:07:27.116369 +0000
+++ blacktest.py        2019-11-23 01:07:30.956945 +0000
@@ -1,10 +1,10 @@
 class Foo:
     def method(self):
         if (
             invalid_reasons := self.invalid_reasons()
-        ):  # pylint: disable=superfluous-parens
+        ) :  # pylint: disable=superfluous-parens
             LOGGER.error(
                 f"Not saving raid for the following reasons: {', '.join(invalid_reasons)}"
             )
             return

[JelleZijlstra]

Agree that this is a bug.