pin_compatible on numpy's numpy-base dependency

Comes from:

# metapackage for things that don't use numpy's C interface, or things
- name: numpy
  requirements:
    build:
      # for runtime alignment
      - {{ compiler('c') }}
      - {{ compiler('fortran') }}
    host:
      - python
    run:
      - python
      - {{ pin_subpackage('numpy-base') }}
      # openblas or mkl runtime included with run_exports
      - mkl_fft # [blas_impl == 'mkl']
      - mkl_random # [blas_impl == 'mkl' and (not win or vc>=14)]

Results in:

The following NEW packages will be INSTALLED:

numpy:           1.11.3-py37h648b28d_9   defaults
numpy-base:      1.15.0-py37h8a80b8c_9   defaults

Fixed by:

# metapackage for things that don't use numpy's C interface, or things
- name: numpy
  requirements:
    build:
      # for runtime alignment
      - {{ compiler('c') }}
      - {{ compiler('fortran') }}
    host:
      - python
    run:
      - python
      - {{ pin_subpackage('numpy-base', exact=True) }}
      # openblas or mkl runtime included with run_exports
      - mkl_fft # [blas_impl == 'mkl']
      - mkl_random # [blas_impl == 'mkl' and (not win or vc>=14)]

lack of blas metapackage dependency

"mkl-devel-2018.0.3-1.tar.bz2": {
  "build": "1",
  "build_number": 1,
  "depends": [
    "mkl 2018.0.3 1",
    "mkl-include 2018.0.3 1",
  ],
  "md5": "86f9ce6e1eb4ec793215939bf460cffc",
  "name": "mkl-devel",
  "sha256": "e49fdacdbf31d37101b447c16b79bc457c8e3c08216930f3d7baea6a168ac7c8",
  "size": 6190,
  "subdir": "linux-64",
  "timestamp": 1528122418745,
  "version": "2018.0.3"
},

leads to things like:

The following NEW packages will be INSTALLED:

blas:            1.0-mkl                 defaults
ca-certificates: 2018.03.07-0            defaults
certifi:         2018.8.13-py37_0        defaults
cython:          0.28.5-py37h0a44026_0   defaults
intel-openmp:    2018.0.3-0              defaults
libcxx:          4.0.1-h579ed51_0        defaults
libcxxabi:       4.0.1-hebd6815_0        defaults
libedit:         3.1.20170329-hb402a30_2 defaults
libffi:          3.2.1-h475c297_4        defaults
libgfortran:     3.0.1-h93005f0_2        defaults
libopenblas:     0.3.2-hdc02c5d_1        local
mkl:             2018.0.3-1              defaults
ncurses:         6.1-h0a44026_0          defaults
nomkl:           2.0-0                   defaults
numpy:           1.11.3-py37h648b28d_9   defaults
numpy-base:      1.11.3-py37h8a80b8c_9   defaults
openblas-devel:  0.3.2-0                 local
openssl:         1.0.2p-h1de35cc_0       defaults
python:          3.7.0-hc167b69_0        defaults
readline:        7.0-hc1231fa_4          defaults
setuptools:      40.0.0-py37_0           defaults
sqlite:          3.24.0-ha441bb4_0       defaults
tk:              8.6.7-h35a86e2_3        defaults
xz:              5.2.4-h1de35cc_4        defaults
zlib:            1.2.11-hf3cbc9b_2       defaults

presence of legacy packages (free channel)

"numpy-1.11.3-py36_nomkl_0.tar.bz2": {
  "build": "py36_nomkl_0",
  "build_number": 0,
  "date": "2017-01-10",
  "depends": [
    "libgfortran 3.0.0",
    "openblas 0.2.19",
    "python 3.6*"
  ],
  "features": "nomkl",
  "license": "BSD",
  "md5": "16df6508002e78e1639ce0416ca76165",
  "name": "numpy",
  "size": 6996427,
  "version": "1.11.3"
},

Conda will find old packages that lack constraints, and sub these in. It is probably best to omit the "free" channel right now:

conda config --add default_channels https://repo.anaconda.com/pkgs/main conda config --add default_channels https://repo.anaconda.com/pkgs/r

On windows, also add:

conda config --add default_channels https://repo.anaconda.com/pkgs/msys2

Processes to fix

rebuilding packages

Does not usually fix the problem. Conda can/will still find old packages and use them when it's not obvious
hard to troubleshoot when old packages are still available

hotfixing metadata

Requires central administration of index (works for defaults, not conda-forge). Work underway to host static index that can be hotfixed for conda-forge via cloudflare.
```
  if record['name'] == 'mkl-devel':
      if not any(d.startswith('blas') for d in record['depends']):
          record['depends'].append("blas * mkl")
```

revoking packages

when new builds are available, but are not getting picked up due to a past metadata mistake
Add an unsatisfiable constraint to effectively remove confusing packages from being picked up
Can add a special channel to make that constraint satisfiable, if you really need the old package
Implementation: for package something-1.0-1.tar.bz2, place a something-1.0-1.tar.bz2.REVOKED file alongside it, and re-run the index command.

msarahan/mistakes.md