Execution failed for task ':clean:'.

I was trying to recompile my mod when suddenly a wild error appeared:

   
Executing gradle command: clean build
Microsoft Windows [Versi¢n 6.1.7601]
Copyright (c) 2009 Microsoft Corporation. All Rights Reserved.
C:\Pylo\MCreator179>cd forge
C:\Pylo\MCreator179\forge>SET "JAVA_HOME=C:\Pylo\MCreator179\jdk\"
C:\Pylo\MCreator179\forge>SET JAVA_EXE=%JAVA_HOME%\bin\java.exe
C:\Pylo\MCreator179\forge>SET PATH=%JAVA_HOME%\bin\;%PATH%
C:\Pylo\MCreator179\forge>SET "GRADLE_USER_HOME=C:\Users\ADMIN\.mcreator\gradle"
C:\Pylo\MCreator179\forge>gradlew -Dorg.gradle.daemon=false -Dorg.gradle.parallel=false -Dorg.gradle.jvmargs="-Xms625m -Xmx2048m" clean build 
This mapping 'snapshot_20171003' was designed for MC 1.12! Use at your own peril.
#################################################
         ForgeGradle 2.3-SNAPSHOT-7764e3e        
  https://github.com/MinecraftForge/ForgeGradle  
#################################################
                 Powered by MCP                  
             http://modcoderpack.com             
     by: Searge, ProfMobius, R4wk, ZeuX          
     Fesh0r, IngisKahn, bspkrs, LexManos         
#################################################
:clean FAILED
FAILURE: Build failed with an exception.
* What went wrong:
Execution failed for task ':clean'.
> Unable to delete file: C:\Pylo\MCreator179\forge\build\retromapping\replacedMain.rangemap
* Try:
BUILD FAILED
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.
Total time: 14.829 secs
C:\Pylo\MCreator179\forge>
Task completed with return code 0 in 16258 milliseconds

What can I do? (I'm using MCreator 1.7.9)