Clean install gives pg_config missing.

[karlcow]

This is not user friendly.
We should either make it possible to use sqlite locally or have a way to install what is required.

webcompat-metrics-server on  140/1 via 🐍 v3.9.1 (venv) 
❯ pip install -r requirements.txt 
Collecting Flask==1.1.2
  Using cached Flask-1.1.2-py2.py3-none-any.whl (94 kB)
Collecting gunicorn==20.0.4
  Using cached gunicorn-20.0.4-py2.py3-none-any.whl (77 kB)
Collecting python-dotenv==0.13.0
  Using cached python_dotenv-0.13.0-py2.py3-none-any.whl (17 kB)
Collecting psycopg2-binary==2.8.5
  Using cached psycopg2-binary-2.8.5.tar.gz (381 kB)
    ERROR: Command errored out with exit status 1:
     command: /Users/karl/code/webcompat-metrics-server/venv/bin/python3 -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'/private/var/folders/yb/mfpz98wx099dbp9ht5bv51d40000gn/T/pip-install-ofa8l30r/psycopg2-binary_ebe334d8982749d8ae1f7752f1fda0ce/setup.py'"'"'; __file__='"'"'/private/var/folders/yb/mfpz98wx099dbp9ht5bv51d40000gn/T/pip-install-ofa8l30r/psycopg2-binary_ebe334d8982749d8ae1f7752f1fda0ce/setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' egg_info --egg-base /private/var/folders/yb/mfpz98wx099dbp9ht5bv51d40000gn/T/pip-pip-egg-info-lxcpeyl5
         cwd: /private/var/folders/yb/mfpz98wx099dbp9ht5bv51d40000gn/T/pip-install-ofa8l30r/psycopg2-binary_ebe334d8982749d8ae1f7752f1fda0ce/
    Complete output (23 lines):
    running egg_info
    creating /private/var/folders/yb/mfpz98wx099dbp9ht5bv51d40000gn/T/pip-pip-egg-info-lxcpeyl5/psycopg2_binary.egg-info
    writing /private/var/folders/yb/mfpz98wx099dbp9ht5bv51d40000gn/T/pip-pip-egg-info-lxcpeyl5/psycopg2_binary.egg-info/PKG-INFO
    writing dependency_links to /private/var/folders/yb/mfpz98wx099dbp9ht5bv51d40000gn/T/pip-pip-egg-info-lxcpeyl5/psycopg2_binary.egg-info/dependency_links.txt
    writing top-level names to /private/var/folders/yb/mfpz98wx099dbp9ht5bv51d40000gn/T/pip-pip-egg-info-lxcpeyl5/psycopg2_binary.egg-info/top_level.txt
    writing manifest file '/private/var/folders/yb/mfpz98wx099dbp9ht5bv51d40000gn/T/pip-pip-egg-info-lxcpeyl5/psycopg2_binary.egg-info/SOURCES.txt'
    
    Error: pg_config executable not found.
    
    pg_config is required to build psycopg2 from source.  Please add the directory
    containing pg_config to the $PATH or specify the full executable path with the
    option:
    
        python setup.py build_ext --pg-config /path/to/pg_config build ...
    
    or with the pg_config option in 'setup.cfg'.
    
    If you prefer to avoid building psycopg2 from source, please install the PyPI
    'psycopg2-binary' package instead.
    
    For further information please check the 'doc/src/install.rst' file (also at
    <https://www.psycopg.org/docs/install.html>).
    
    ----------------------------------------
WARNING: Discarding https://files.pythonhosted.org/packages/97/00/ed4c82364741031d745867f83820d4f373aa891098a5785841850491c9ba/psycopg2-binary-2.8.5.tar.gz#sha256=ccdc6a87f32b491129ada4b87a43b1895cf2c20fdb7f98ad979647506ffc41b6 (from https://pypi.org/simple/psycopg2-binary/) (requires-python:>=2.7,!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*). Command errored out with exit status 1: python setup.py egg_info Check the logs for full command output.
ERROR: Could not find a version that satisfies the requirement psycopg2-binary==2.8.5
ERROR: No matching distribution found for psycopg2-binary==2.8.5