El paquete está instalado y no se detecta. (gradle)

Question

Instalé gradle de la forma típica:

sudo apt install gradle
Reading package lists... Done
Building dependency tree       
Reading state information... Done
gradle is already the newest version (3.5-0ubuntu1).
0 to upgrade, 0 to newly install, 0 to remove and 8 not to upgrade.

A continuación quería utilizar este programa:

$ gradle 
The program 'gradle' is currently not installed. You can install it by typing:
sudo apt install gradle

Estaba intentando eliminar Java, purgar Gradle, eliminarlo de cualquier lugar e instalarlo nuevamente. Nada ayuda... Lo más confuso es que este paquete funcionaba correctamente unos días antes sin problemas.

A continuación algunas depuraciones:

$ which gradle
$ whereis gradle
gradle:
$ apt-cache policy gradle
gradle:
  Installed: 3.5-0ubuntu1
  Candidate: 3.5-0ubuntu1
  Version table:
 *** 3.5-0ubuntu1 500
        500 http://ppa.launchpad.net/cwchien/gradle/ubuntu xenial/main amd64 Packages
        500 http://ppa.launchpad.net/cwchien/gradle/ubuntu xenial/main i386 Packages
        100 /var/lib/dpkg/status
     2.10-1 500
        500 http://archive.ubuntu.com/ubuntu xenial/universe amd64 Packages
        500 http://archive.ubuntu.com/ubuntu xenial/universe i386 Packages
     1.4-2ubuntu1 500
        500 http://us.archive.ubuntu.com/ubuntu trusty/universe amd64 Packages
        500 http://us.archive.ubuntu.com/ubuntu trusty/universe i386 Packages

¿Cómo revertir el sistema al estado en el que este paquete se detectará correctamente?

Actualizar

Encontré el comando:

sudo apt-get clean

Ahora obtengo:

sudo apt install gradle
Reading package lists... Done
Building dependency tree       
Reading state information... Done
gradle is already the newest version (3.5-0ubuntu1).
0 to upgrade, 0 to newly install, 0 to remove and 8 not to upgrade.
W: Target Packages (main/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list:7 and /etc/apt/sources.list.d/docker.list:1
W: Target Packages (main/binary-all/Packages) is configured multiple times in /etc/apt/sources.list:7 and /etc/apt/sources.list.d/docker.list:1
W: Target Translations (main/i18n/Translation-en_GB) is configured multiple times in /etc/apt/sources.list:7 and /etc/apt/sources.list.d/docker.list:1
W: Target Translations (main/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list:7 and /etc/apt/sources.list.d/docker.list:1
W: Target Translations (main/i18n/Translation-pl) is configured multiple times in /etc/apt/sources.list:7 and /etc/apt/sources.list.d/docker.list:1
W: Target DEP-11 (main/dep11/Components-amd64.yml) is configured multiple times in /etc/apt/sources.list:7 and /etc/apt/sources.list.d/docker.list:1
W: Target DEP-11-icons (main/dep11/icons-64x64.tar) is configured multiple times in /etc/apt/sources.list:7 and /etc/apt/sources.list.d/docker.list:1

Actualización2

dpkg -L gradle
/.
/usr
/usr/share
/usr/share/doc
/usr/share/doc/gradle
/usr/share/doc/gradle/changelog.Debian.gz
/usr/share/doc/gradle/copyright

namei -lx /usr/bin/gradle
f: /usr/bin/gradle
Drwxr-xr-x root root /
drwxr-xr-x root root usr
drwxr-xr-x root root bin
                     gradle - No such file or directory

Answer 1

Finalmente gracias a los comentarios de @muru realicé los siguientes pasos:

Quite ppa:cwchien/gradle:

sudo rm -rf /etc/apt/sources.list.d/cwchien-ubuntu-gradle-xenial.*
sudo apt-get update

Instalé el antiguo gradle desde el repositorio oficial:

sudo apt-get install gradle

Entonces todas las dependencias se instalaron correctamente. Luego agrego cwchien-ubuntu-gradle-xenialnuevamente y lo instalé nuevamente:

sudo apt-get install gradle-ppa gradle

Finalmente en el sitio webhttps://gradle.org/installEncontré el comando:

export PATH=$PATH:/opt/gradle/gradle-3.5/bin

Eso finalmente resolvió mis problemas, y ahora:

gradle -v

------------------------------------------------------------
Gradle 3.5
------------------------------------------------------------

Actualizar

Ahora estoy instalando gradle porsdkman.iopor estos comandos:

Instalar sdkman

curl -s "https://get.sdkman.io" | bash 

Instalar gradle

sdk install gradle 4.0.2