Remove dependency on PyScaffold during builds

As discussed in pyscaffold#256, after pytest-runner was deprecated and removed,
the only strong reason for having PyScaffold required during builds is
to use setuptools_scm. Docs can easily be generated via Makefile
(already created by default) or tox/nox (the new tox template already
contains a task for the docs).

A way of removing this dependency is by injecting setuptools_scm
directly on the `setup.py` template. In the future something similar can
be done for `pyproject.toml` (when it is generated by default).

This change is an attempt of doing that. As a direct consequence, we
also remove PyScaffold as a build-time dependency of itself, which makes
things easier.

setup.cfg

@@ -36,7 +36,14 @@ python_requires = >=3.6
 include_package_data = True
 package_dir =
     =src
-install_requires = setuptools>=38.3
+setup_requires =
+    setuptools_scm>=4.1.2,<5.0
+    wheel>=0.34.2,<1.0
+install_requires =
+    appdirs>=1.4.4,<2.0
+    configupdater>=1.0.1,<2.0
+    setuptools_scm>=4.1.2,<5.0
+    setuptools>=38.3
 
 [options.packages.find]
 where = src
@@ -83,31 +90,6 @@ pyscaffold.cli =
     travis = pyscaffold.extensions.travis:Travis
     gitlab = pyscaffold.extensions.gitlab_ci:GitLab
     cirrus = pyscaffold.extensions.cirrus:Cirrus
-setuptools.file_finders =
-    setuptools_scm = pyscaffold.contrib.setuptools_scm.integration:find_files
-setuptools_scm.parse_scm =
-    .hg = pyscaffold.contrib.setuptools_scm.hg:parse
-    .git = pyscaffold.contrib.setuptools_scm.git:parse
-setuptools_scm.parse_scm_fallback =
-    .hg_archival.txt = pyscaffold.contrib.setuptools_scm.hg:parse_archival
-    PKG-INFO = pyscaffold.contrib.setuptools_scm.hacks:parse_pkginfo
-    pip-egg-info = pyscaffold.contrib.setuptools_scm.hacks:parse_pip_egg_info
-setuptools_scm.files_command =
-    .hg = pyscaffold.contrib.setuptools_scm.file_finder_hg:hg_find_files
-    .git = pyscaffold.contrib.setuptools_scm.file_finder_git:git_find_files
-setuptools_scm.version_scheme =
-    guess-next-dev = pyscaffold.contrib.setuptools_scm.version:guess_next_dev_version
-    post-release = pyscaffold.contrib.setuptools_scm.version:postrelease_version
-    python-simplified-semver = setuptools_scm.version:simplified_semver_version
-setuptools_scm.local_scheme =
-    node-and-date = pyscaffold.contrib.setuptools_scm.version:get_local_node_and_date
-    node-and-timestamp = pyscaffold.contrib.setuptools_scm.version:get_local_node_and_timestamp
-    dirty-tag = pyscaffold.contrib.setuptools_scm.version:get_local_dirty_tag
-
-[test]
-# py.test options when running `python setup.py test`
-addopts = --verbose
-extras = True
 
 [tool:pytest]
 # Options for py.test:
@@ -137,11 +119,6 @@ log_cli_level = CRITICAL
 [aliases]
 dists = sdist bdist_wheel
 
-[build_sphinx]
-# Options for Sphinx build
-source_dir = docs
-build_dir = build/sphinx
-
 [devpi:upload]
 # Options for the devpi: PyPI server and packaging tool
 # VCS export must be deactivated since we are using setuptools-scm

setup.py

@@ -1,62 +1,16 @@
 # -*- coding: utf-8 -*-
-"""
-    Setup file for PyScaffold.
-
-    Important note: Since PyScaffold is self-using and depends on
-    setuptools-scm, it is important to run:
-    `python setup.py egg_info --egg-base .`
-    after a fresh checkout. This will generate some critically needed data.
-"""
-import inspect
-import os
+"""Setup file for PyScaffold."""
 import sys
 
+from pkg_resources import VersionConflict, require
 from setuptools import setup
 
-__location__ = os.path.join(
-    os.getcwd(), os.path.dirname(inspect.getfile(inspect.currentframe()))
-)
-
-
-def bootstrap_cfg():
-    """Allow PyScaffold to be used to package itself.
-
-    Usually, running ``python setup.py egg_info --egg-base .`` first is a good
-    idea.
-    """
-    src_dir = os.path.join(__location__, "src")
-    egg_info_dir = os.path.join(__location__, "PyScaffold.egg-info")
-    has_entrypoints = os.path.isdir(egg_info_dir)
-    import pkg_resources
-
-    sys.path.insert(0, src_dir)
-    pkg_resources.working_set.add_entry(src_dir)
-    from pyscaffold.contrib.setuptools_scm import get_version
-    from pyscaffold.contrib.setuptools_scm.git import parse as parse_git
-    from pyscaffold.contrib.setuptools_scm.hacks import parse_pkginfo
-    from pyscaffold.integration import local_version2str, version2str
-    from pyscaffold.utils import check_setuptools_version
-
-    check_setuptools_version()
-
-    def parse(root):
-        try:
-            return parse_pkginfo(root)
-        except IOError:
-            return parse_git(root)
-
-    config = dict(version_scheme=version2str, local_scheme=local_version2str,)
-
-    if has_entrypoints:
-        return dict(use_pyscaffold=True)
-    else:
-        return dict(version=get_version(root=__location__, parse=parse, **config))
-
-
-def setup_package():
-    """Call setuptools-provided `setup` using PyScaffold to bootstrap itself"""
-    setup(**bootstrap_cfg())
+try:
+    require("setuptools>=38.3")
+except VersionConflict:
+    print("Error: version of setuptools is too old (<38.3)!")
+    sys.exit(1)
 
 
 if __name__ == "__main__":
-    setup_package()
+    setup(use_scm_version={"version_scheme": "post-release"})