title: Not able to install scanpy package using conda install or pip
body: <p>I have been trying to install scanpy package in anaconda using</p>
  <pre><code>conda install scanpy
  </code></pre>
  <p>it did not work for some unsatisfiable error. Then I tried to use</p>
  <pre><code>pip install scanpy
  </code></pre>
  <p>it gave me an error involving <code>llvmlite</code>
  I installed llvmlite too but it is still not working. it shows me following error.</p>
  <pre><code>    Building wheel for llvmlite (setup.py) ... error
    ERROR: Command errored out with exit status 1:
     command: /media/asif/LocalDisc1/anaconda3/envs/scRNAseq/bin/python3.9 -u -c 'import sys, setuptools, tokenize; sys.argv[0] = '&quot;'&quot;'/tmp/pip-install-jau3fq4a/llvmlite_c960ef5cb4c84cd089c0efb72aecc497/setup.py'&quot;'&quot;'; __file__='&quot;'&quot;'/tmp/pip-install-jau3fq4a/llvmlite_c960ef5cb4c84cd089c0efb72aecc497/setup.py'&quot;'&quot;';f=getattr(tokenize, '&quot;'&quot;'open'&quot;'&quot;', open)(__file__);code=f.read().replace('&quot;'&quot;'\r\n'&quot;'&quot;', '&quot;'&quot;'\n'&quot;'&quot;');f.close();exec(compile(code, __file__, '&quot;'&quot;'exec'&quot;'&quot;'))' bdist_wheel -d /tmp/pip-wheel-kgjl38x2
         cwd: /tmp/pip-install-jau3fq4a/llvmlite_c960ef5cb4c84cd089c0efb72aecc497/
    Complete output (26 lines):
    running bdist_wheel
    /media/asif/LocalDisc1/anaconda3/envs/scRNAseq/bin/python3.9 /tmp/pip-install-jau3fq4a/llvmlite_c960ef5cb4c84cd089c0efb72aecc497/ffi/build.py
    LLVM version... Traceback (most recent call last):
      File &quot;/tmp/pip-install-jau3fq4a/llvmlite_c960ef5cb4c84cd089c0efb72aecc497/ffi/build.py&quot;, line 105, in main_posix
        out = subprocess.check_output([llvm_config, '--version'])
      File &quot;/media/asif/LocalDisc1/anaconda3/envs/scRNAseq/lib/python3.9/subprocess.py&quot;, line 420, in check_output
        return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,
      File &quot;/media/asif/LocalDisc1/anaconda3/envs/scRNAseq/lib/python3.9/subprocess.py&quot;, line 501, in run
        with Popen(*popenargs, **kwargs) as process:
      File &quot;/media/asif/LocalDisc1/anaconda3/envs/scRNAseq/lib/python3.9/subprocess.py&quot;, line 947, in __init__
        self._execute_child(args, executable, preexec_fn, close_fds,
      File &quot;/media/asif/LocalDisc1/anaconda3/envs/scRNAseq/lib/python3.9/subprocess.py&quot;, line 1819, in _execute_child
        raise child_exception_type(errno_num, err_msg, err_filename)
    FileNotFoundError: [Errno 2] No such file or directory: 'llvm-config'
    
    During handling of the above exception, another exception occurred:
    
    Traceback (most recent call last):
      File &quot;/tmp/pip-install-jau3fq4a/llvmlite_c960ef5cb4c84cd089c0efb72aecc497/ffi/build.py&quot;, line 191, in &lt;module&gt;
        main()
      File &quot;/tmp/pip-install-jau3fq4a/llvmlite_c960ef5cb4c84cd089c0efb72aecc497/ffi/build.py&quot;, line 181, in main
        main_posix('linux', '.so')
      File &quot;/tmp/pip-install-jau3fq4a/llvmlite_c960ef5cb4c84cd089c0efb72aecc497/ffi/build.py&quot;, line 107, in main_posix
        raise RuntimeError(&quot;%s failed executing, please point LLVM_CONFIG &quot;
    RuntimeError: llvm-config failed executing, please point LLVM_CONFIG to the path for llvm-config
    error: command '/media/asif/LocalDisc1/anaconda3/envs/scRNAseq/bin/python3.9' failed with exit code 1
    ----------------------------------------
    ERROR: Failed building wheel for llvmlite
  </code></pre>