In this post, I’ll resolve an error that one might face when trying to install the minerl Python package. The instructions to install this package can be found here.

  1. Using the instructions above, when I used the install command (pip3 install git+https://github.com/minerllabs/minerl), I got the following error (only the relevant part is shown here):
          Note: Some input files use or override a deprecated API.
      Note: Recompile with -Xlint:deprecation for details.
      Note: Some input files use unchecked or unsafe operations.
      Note: Recompile with -Xlint:unchecked for details.
      100 errors
      only showing the first 100 errors, of 2866 total; use -Xmaxerrs if you would like to see more

      > Task :compileJava FAILED

      FAILURE: Build failed with an exception.

      * What went wrong:
      Execution failed for task ':compileJava'.
      > Compilation failed; see the compiler error output for details.

      * Try:
      Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

      * Get more help at https://help.gradle.org

      Deprecated Gradle features were used in this build, making it incompatible with Gradle 7.0.
      Use '--warning-mode all' to show the individual deprecation warnings.
      See https://docs.gradle.org/6.8.1/userguide/command_line_interface.html#sec:command_line_warnings

      BUILD FAILED in 21s
      10 actionable tasks: 10 executed
      Traceback (most recent call last):
        File "<string>", line 2, in <module>
        File "<pip-setuptools-caller>", line 34, in <module>
        File "/private/var/folders/ly/3d_s7td56qb7rn4qc2c6tmvm0000gn/T/pip-req-build-9xj7s1on/setup.py", line 214, in <module>
          prep_mcp()
        File "/private/var/folders/ly/3d_s7td56qb7rn4qc2c6tmvm0000gn/T/pip-req-build-9xj7s1on/setup.py", line 198, in prep_mcp
          subprocess.check_call('{} clean build shadowJar'.format(gradlew).split(' '), cwd=workdir)
        File "/Users/<username>/.pyenv/versions/3.11.2/lib/python3.11/subprocess.py", line 413, in check_call
          raise CalledProcessError(retcode, cmd)
      subprocess.CalledProcessError: Command '['./gradlew', 'clean', 'build', 'shadowJar']' returned non-zero exit status 1.
      [end of output]

  note: This error originates from a subprocess, and is likely not a problem with pip.
error: metadata-generation-failed

  1. Searching for the error message (error: metadata-generation-failed) took me to a bunch of websites that provided other options to try:

    • From the install page, I tried providing the --user option in the install command, that did not work, and I got the same error. This was the command I used: pip3 install git+https://github.com/minerllabs/minerl --user
    • From this stackoverflow page, I used the --pre option in the install command, that didn’t work either. This was the command I used: pip3 install git+https://github.com/minerllabs/minerl --pre
    • From this page, I learnt about using the --use-deprecated option, but that did not work too. This was the command I used: pip3 install git+https://github.com/minerllabs/minerl --use-deprecated=legacy-resolver

  2. Going back to the minerl install page, I checked the Java version, hoping that this was the issue:

      $ java -version
      openjdk version "14.0.2" 2020-07-14
      OpenJDK Runtime Environment (build 14.0.2+12-46)
      OpenJDK 64-Bit Server VM (build 14.0.2+12-46, mixed mode, sharing)
  1. My system was using the wrong version of Java (it should be using 1.8._)! I used the instructions here, to remove the other version of Java. These were the exact commands I used:
      $ sudo rm -fr /Library/Java/JavaVirtualMachines/openjdk-14.0.2.jdk/
      $ sudo rm -fr /Library/Internet\ Plug-Ins/JavaAppletPlugin.plugin
      $ sudo rm -fr /Library/PreferencePanes/JavaControlPanel.prefPane
  1. If you encounter this error on a macOS, and the Java version is the cause, check your Java version using the java -version command on terminal, and navigate to the /Library/Java/JavaVirtualMachines/ folder to find the other versions of Java on your machine. Then use the sudo commands above to delete the appropriate folders. After deleting the other Java folder on my machine, typing java -version in my terminal gave me the following result:
      $ java -version
      openjdk version "1.8.0_292"
      OpenJDK Runtime Environment (AdoptOpenJDK)(build 1.8.0_292-b10)
      OpenJDK 64-Bit Server VM (AdoptOpenJDK)(build 25.292-b10, mixed mode)
  1. After doing this, the install command (pip3 install git+https://github.com/minerllabs/minerl), worked fine on the terminal. I did see some error messages (around installation of the Python package gym), but it didn’t appear to affect the installation:
    Failed to build gym
    Installing collected packages: PyWavelets, Pyro4, opencv-python, matplotlib-inline, lxml, 
    jinja2, jedi, inflection, idna, humanfriendly, flaky, dill, decorator, cloudpickle, charset-normalizer, 
    certifi, asttokens, stack-data, requests, imagehash, gym, coloredlogs, ipython, minerl
      Running setup.py install for gym ... done
      DEPRECATION: gym was installed using the legacy 'setup.py install'
      method, because a wheel could not be built for it. pip 23.1 will enforce this behaviour change. 
      A possible replacement is to fix the wheel build issue reported above.
      Discussion can be found at https://github.com/pypa/pip/issues/8368
  1. Create your first agent and check if everything is working properly. If the example linked does not work, refer to this post, or this github issue comment.