Warning during installation with clean docker image

Building on clean docker image python:3.9.6-buster

```Dockerfile
FROM python:3.9.6-buster

RUN pip install cython plotly numpy xlrd pandas requests pytz uuid matplotlib tqdm scikit-learn seaborn scipy \
&& pip install 'bokeh<2.0.0' \
&& pip install prophet
```

Warning log

```logs
Collecting prophet
Downloading prophet-1.0.1.tar.gz (65 kB)
Requirement already satisfied: Cython>=0.22 in /usr/local/lib/python3.9/site-packages (from prophet) (0.29.24)
Collecting cmdstanpy==0.9.68
Downloading cmdstanpy-0.9.68-py3-none-any.whl (49 kB)
Collecting pystan~=2.19.1.1
Downloading pystan-2.19.1.1.tar.gz (16.2 MB)
Requirement already satisfied: numpy>=1.15.4 in /usr/local/lib/python3.9/site-packages (from prophet) (1.21.1)
Requirement already satisfied: pandas>=1.0.4 in /usr/local/lib/python3.9/site-packages (from prophet) (1.3.1)
Requirement already satisfied: matplotlib>=2.0.0 in /usr/local/lib/python3.9/site-packages (from prophet) (3.4.2)
Collecting LunarCalendar>=0.0.9
Downloading LunarCalendar-0.0.9-py2.py3-none-any.whl (18 kB)
Collecting convertdate>=2.1.2
Downloading convertdate-2.3.2-py3-none-any.whl (47 kB)
Collecting holidays>=0.10.2
Downloading holidays-0.11.2-py3-none-any.whl (142 kB)
Collecting setuptools-git>=1.2
Downloading setuptools_git-1.2-py2.py3-none-any.whl (10 kB)
Requirement already satisfied: python-dateutil>=2.8.0 in /usr/local/lib/python3.9/site-packages (from prophet) (2.8.2)
Requirement already satisfied: tqdm>=4.36.1 in /usr/local/lib/python3.9/site-packages (from prophet) (4.61.2)
Collecting ujson
Downloading ujson-4.0.2-cp39-cp39-manylinux1_x86_64.whl (179 kB)
Requirement already satisfied: pytz>=2014.10 in /usr/local/lib/python3.9/site-packages (from convertdate>=2.1.2->prophet) (2021.1)
Collecting pymeeus<=1,>=0.3.13
Downloading PyMeeus-0.5.11.tar.gz (5.4 MB)
Collecting hijri-converter
Downloading hijri_converter-2.1.3-py3-none-any.whl (14 kB)
Collecting korean-lunar-calendar
Downloading korean_lunar_calendar-0.2.1-py3-none-any.whl (8.0 kB)
Requirement already satisfied: six in /usr/local/lib/python3.9/site-packages (from holidays>=0.10.2->prophet) (1.16.0)
Collecting ephem>=3.7.5.3
Downloading ephem-4.0.0.2-cp39-cp39-manylinux2010_x86_64.whl (1.2 MB)
Requirement already satisfied: pyparsing>=2.2.1 in /usr/local/lib/python3.9/site-packages (from matplotlib>=2.0.0->prophet) (2.4.7)
Requirement already satisfied: cycler>=0.10 in /usr/local/lib/python3.9/site-packages (from matplotlib>=2.0.0->prophet) (0.10.0)
Requirement already satisfied: kiwisolver>=1.0.1 in /usr/local/lib/python3.9/site-packages (from matplotlib>=2.0.0->prophet) (1.3.1)
Requirement already satisfied: pillow>=6.2.0 in /usr/local/lib/python3.9/site-packages (from matplotlib>=2.0.0->prophet) (8.3.1)
Building wheels for collected packages: prophet, pymeeus, pystan
Building wheel for prophet (setup.py): started
Building wheel for prophet (setup.py): finished with status 'error'
ERROR: Command errored out with exit status 1:
command: /usr/local/bin/python -u -c 'import io, os, sys, setuptools, tokenize; sys.argv[0] = '"'"'/tmp/pip-install-qbsnyz58/prophet_4eb77a6d036e41b29b6e60177b757235/setup.py'"'"'; __file__='"'"'/tmp/pip-install-qbsnyz58/prophet_4eb77a6d036e41b29b6e60177b757235/setup.py'"'"';f = getattr(tokenize, '"'"'open'"'"', open)(__file__) if os.path.exists(__file__) else io.StringIO('"'"'from setuptools import setup; setup()'"'"');code = f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' bdist_wheel -d /tmp/pip-wheel-n3f90iz5
cwd: /tmp/pip-install-qbsnyz58/prophet_4eb77a6d036e41b29b6e60177b757235/
Complete output (44 lines):
running bdist_wheel
running build
running build_py
creating build
creating build/lib
creating build/lib/prophet
creating build/lib/prophet/stan_model
Traceback (most recent call last):
File "", line 1, in
File "/tmp/pip-install-qbsnyz58/prophet_4eb77a6d036e41b29b6e60177b757235/setup.py", line 123, in
setup(
File "/usr/local/lib/python3.9/site-packages/setuptools/__init__.py", line 153, in setup
return distutils.core.setup(**attrs)
File "/usr/local/lib/python3.9/distutils/core.py", line 148, in setup
dist.run_commands()
File "/usr/local/lib/python3.9/distutils/dist.py", line 966, in run_commands
self.run_command(cmd)
File "/usr/local/lib/python3.9/distutils/dist.py", line 985, in run_command
cmd_obj.run()
File "/usr/local/lib/python3.9/site-packages/wheel/bdist_wheel.py", line 299, in run
self.run_command('build')
File "/usr/local/lib/python3.9/distutils/cmd.py", line 313, in run_command
self.distribution.run_command(command)
File "/usr/local/lib/python3.9/distutils/dist.py", line 985, in run_command
cmd_obj.run()
File "/usr/local/lib/python3.9/distutils/command/build.py", line 135, in run
self.run_command(cmd_name)
File "/usr/local/lib/python3.9/distutils/cmd.py", line 313, in run_command
self.distribution.run_command(command)
File "/usr/local/lib/python3.9/distutils/dist.py", line 985, in run_command
cmd_obj.run()
File "/tmp/pip-install-qbsnyz58/prophet_4eb77a6d036e41b29b6e60177b757235/setup.py", line 48, in run
build_models(target_dir)
File "/tmp/pip-install-qbsnyz58/prophet_4eb77a6d036e41b29b6e60177b757235/setup.py", line 36, in build_models
from prophet.models import StanBackendEnum
File "/tmp/pip-install-qbsnyz58/prophet_4eb77a6d036e41b29b6e60177b757235/prophet/__init__.py", line 8, in
from prophet.forecaster import Prophet
File "/tmp/pip-install-qbsnyz58/prophet_4eb77a6d036e41b29b6e60177b757235/prophet/forecaster.py", line 17, in
from prophet.make_holidays import get_holiday_names, make_holidays_df
File "/tmp/pip-install-qbsnyz58/prophet_4eb77a6d036e41b29b6e60177b757235/prophet/make_holidays.py", line 14, in
import prophet.hdays as hdays_part2
File "/tmp/pip-install-qbsnyz58/prophet_4eb77a6d036e41b29b6e60177b757235/prophet/hdays.py", line 13, in
from convertdate.islamic import from_gregorian, to_gregorian
ModuleNotFoundError: No module named 'convertdate'
----------------------------------------
ERROR: Failed building wheel for prophet
Running setup.py clean for prophet
Building wheel for pymeeus (setup.py): started
Building wheel for pymeeus (setup.py): finished with status 'done'
Created wheel for pymeeus: filename=PyMeeus-0.5.11-py3-none-any.whl size=730983 sha256=ed96a75c810a83b4c7ca554bda4ddf621d98627e1c96e133ffc56b41c1e1c9bd
Stored in directory: /root/.cache/pip/wheels/33/3d/82/4579e9cca41ff991140b2e050bc6df3a38292f26e4fa06b15d
Building wheel for pystan (setup.py): started
Building wheel for pystan (setup.py): still running...
Building wheel for pystan (setup.py): still running...
Building wheel for pystan (setup.py): finished with status 'done'
Created wheel for pystan: filename=pystan-2.19.1.1-cp39-cp39-linux_x86_64.whl size=61829149 sha256=3348ac7ade5e2ccb74c14f93cdfe07ce390c3edab083f6f5b22c950cde5ad2b8
Stored in directory: /root/.cache/pip/wheels/b8/36/bf/7ec7e363f796373cea3eb9ea94e83f5bbbb586d2edbf7e3417
Successfully built pymeeus pystan
Failed to build prophet
Installing collected packages: pymeeus, ujson, korean-lunar-calendar, hijri-converter, ephem, convertdate, setuptools-git, pystan, LunarCalendar, holidays, cmdstanpy, prophet
Running setup.py install for prophet: started
Running setup.py install for prophet: still running...
Running setup.py install for prophet: finished with status 'done'
DEPRECATION: prophet was installed using the legacy 'setup.py install' method, because a wheel could not be built for it. A possible replacement is to fix the wheel build issue reported above. You can find discussion regarding this at https://github.com/pypa/pip/issues/8368.

```

https://github.com/pypa/pip/issues/8368#issuecomment-888932590