Merge tag 'v5.2.1' into develop

Bump version to 5.2.1

HISTORY.rst

@@ -8,7 +8,7 @@ PlatformIO Core 5
 
 **A professional collaborative platform for embedded development**
 
-5.2.1 (2021-??-??)
+5.2.1 (2021-10-11)
 ~~~~~~~~~~~~~~~~~~
 
 - Clean a build environment and installed library dependencies using a new ``cleanall`` target (`issue #4062 <https://github.com/platformio/platformio-core/issues/4062>`_)
@@ -20,7 +20,6 @@ PlatformIO Core 5
 - Fixed a "FileExist" error when the `platformio ci <https://docs.platformio.org/en/latest/userguide/cmd_ci.html>`__ command is used in pair with the ``--keep-build-dir`` option (`issue #4011 <https://github.com/platformio/platformio-core/issues/4011>`_)
 - Fixed an issue with draft values of C++ language standards that broke static analysis via Cppcheck (`issue #3944 <https://github.com/platformio/platformio-core/issues/3944>`_)
 
-
 5.2.0 (2021-09-13)
 ~~~~~~~~~~~~~~~~~~
 

platformio/__init__.py

@@ -14,7 +14,7 @@
 
 import sys
 
-VERSION = (5, 2, "1rc2")
+VERSION = (5, 2, 1)
 __version__ = ".".join([str(s) for s in VERSION])
 
 __title__ = "platformio"