title: Error installing eth-brownie. (with pipx)
body: <p>Tried installing with <code>pipx install brownie</code>
  After the error below, I also tried <code>pipx install cytoolz</code> to no avail. fml.</p>
  <pre><code>pip failed to build package:
      cytoolz
  
  Some possibly relevant errors from pip install:
      cytoolz/functoolz.c:23087:19: error: implicit declaration of function '_PyGen_Send' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
      cytoolz/functoolz.c:23092:19: error: implicit declaration of function '_PyGen_Send' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
      cytoolz/functoolz.c:23176:19: error: implicit declaration of function '_PyGen_Send' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
      error: command '/usr/bin/clang' failed with exit code 1
  
  Error installing eth-brownie.
  </code></pre>
  <p>Help appreciated!</p>