NameError: name 'speclite' is not defined

[Lucia-Fonseca]

Describe the bug
The problem occurs when the SkyPy pipeline tries to execute the skypy.galaxies.spectrum.kcorrect.stellar_mass function (line 18 in galaxies.yaml):

cosmology: !astropy.cosmology.FlatLambdaCDM
  H0: 70
  Om0: 0.3
tables:
  SF:
    z, M_B: !skypy.galaxies.schechter_lf
      redshift: !numpy.geomspace [0.01, 3.01, 3]
      M_star: -20.485
      phi_star: 0.00312608
      alpha: -1.29
      m_lim: 30
      sky_area: 10 deg2
    coeff: !skypy.galaxies.spectrum.dirichlet_coefficients
      redshift: $SF.z
      alpha0: [2.079, 3.524, 1.917, 1.992, 2.536]
      alpha1: [2.265, 3.862, 1.921, 1.685, 2.480]
      weight: [3.47e+09, 3.31e+06, 2.13e+09, 1.64e+10, 1.01e+09]
    sm: !skypy.galaxies.spectrum.kcorrect.stellar_mass
      coefficients: $SF.coeff
      magnitudes: $SF.M_B
      filter: bessell-B

To Reproduce

1. From a fresh environment, I installed SkyPy 0.4 and the latest version of Python 3.8.5
2. In a Jupyter notebook, I imported SkyPy.pipeline.Pipeline
3. I ran the code

   >>> from skypy.pipeline import Pipeline
   >>> sim = Pipeline.read('galaxies.yaml')
   >>> sim.execute()

4. Got error NameError: name 'speclite' is not defined.

Expected behaviour
I would expect SkyPy to install all dependencies. However, since this is an optional package, I would expect to raise and ImportError.

System Details
macOS-11.2.1
Python 3.8.5 (default, Sep 4 2020, 02:22:02)
SkyPy 0.4

Solution
I installed the speclite package
python3 -m pip install speclite
and the error disappeared.

[rrjbca]

@Lucia-Fonseca could you please add an explanation of how to reproduce the bug? Ideally a step by step including what skypy version you have installed, what python script / config files you used, the traceback and (how) were you able to resolve the error?

[rrjbca]

@Lucia-Fonseca what is the contents of galaxies.yml? Can you provide a minimal working example?

[rrjbca]

Minimal working example:

>>> from skypy.utils.photometry import mag_ab
>>> import numpy as np
>>> mag_ab(np.linspace(1,10,100), np.ones(100), 'bessell-B')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "skypy/utils/photometry.py", line 91, in mag_ab
    filters = speclite.filters.load_filters(*filters)
NameError: name 'speclite' is not defined