setuptools doesn't have a formal understanding of development requires,
but it has an optional feataures section. Fine; add a "devel" feature
and add the requirements to it.

To avoid duplication, we can modify pipenv to install qemu[devel]
instead. This enables us to run invocations like "pip install -e
.[devel]" and test the package on bleeding-edge packages beyond those
specified in Pipfile.lock.

Importantly, this also allows us to install the qemu development
packages in a non-networked mode: `pip3 install --no-index -e .[devel]`
will now fail if the proper development dependencies are not already
met. This can be useful for automated build scripts where fetching
network packages may be undesirable.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Cleber Rosa <crosa@redhat.com>
---
 python/PACKAGE.rst  |  4 ++++
 python/README.rst   |  4 ++++
 python/Pipfile      |  5 +----
 python/Pipfile.lock | 14 +++++++++-----
 python/setup.cfg    |  9 +++++++++
 5 files changed, 27 insertions(+), 9 deletions(-)

diff --git a/python/PACKAGE.rst b/python/PACKAGE.rst
index 1bbfe1b58e2..05ea7789fc1 100644
--- a/python/PACKAGE.rst
+++ b/python/PACKAGE.rst
@@ -31,3 +31,7 @@ official `GitLab mirror <https://gitlab.com/qemu-project/qemu>`_.
 Please report bugs on the `QEMU issue tracker
 <https://gitlab.com/qemu-project/qemu/-/issues>`_ and tag ``@jsnow`` in
 the report.
+
+Optional packages necessary for running code quality analysis for this
+package can be installed with the optional dependency group "devel":
+``pip install qemu[devel]``.
diff --git a/python/README.rst b/python/README.rst
index bf9bbca979a..954870973d0 100644
--- a/python/README.rst
+++ b/python/README.rst
@@ -24,6 +24,10 @@ which installs a version of the package that installs a forwarder
 pointing to these files, such that the package always reflects the
 latest version in your git tree.
 
+Installing ".[devel]" instead of "." will additionally pull in required
+packages for testing this package. They are not runtime requirements,
+and are not needed to simply use these libraries.
+
 See `Installing packages using pip and virtual environments
 <https://packaging.python.org/guides/installing-using-pip-and-virtual-environments/>`_
 for more information.
diff --git a/python/Pipfile b/python/Pipfile
index dbe96f71c48..e7acb8cefa4 100644
--- a/python/Pipfile
+++ b/python/Pipfile
@@ -4,10 +4,7 @@ url = "https://pypi.org/simple"
 verify_ssl = true
 
 [dev-packages]
-flake8 = ">=3.6.0"
-isort = ">=5.1.2"
-mypy = ">=0.770"
-pylint = ">=2.8.0"
+qemu = {editable = true, extras = ["devel"], path = "."}
 
 [packages]
 qemu = {editable = true,path = "."}
diff --git a/python/Pipfile.lock b/python/Pipfile.lock
index f0bf576c31e..a2cdc1c50ea 100644
--- a/python/Pipfile.lock
+++ b/python/Pipfile.lock
@@ -1,7 +1,7 @@
 {
     "_meta": {
         "hash": {
-            "sha256": "7c74cc4c2db3a75c954a6686411cda6fd60e464620bb6d5f1ed9a54be61db4cc"
+            "sha256": "eff562a688ebc6f3ffe67494dbb804b883e2159ad81c4d55d96da9f7aec13e91"
         },
         "pipfile-spec": 6,
         "requires": {
@@ -35,7 +35,7 @@
                 "sha256:07528381786f2a6237b061f6e96610a4167b226cb926e2aa2b6b1d78057c576b",
                 "sha256:bf8fd333346d844f616e8d47905ef3a3384edae6b4e9beb0c5101e25e3110907"
             ],
-            "index": "pypi",
+            "markers": "python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3, 3.4'",
             "version": "==3.9.2"
         },
         "importlib-metadata": {
@@ -51,7 +51,7 @@
                 "sha256:0a943902919f65c5684ac4e0154b1ad4fac6dcaa5d9f3426b732f1c8b5419be6",
                 "sha256:2bb1680aad211e3c9944dbce1d4ba09a989f04e238296c87fe2139faa26d655d"
             ],
-            "index": "pypi",
+            "markers": "python_version >= '3.6' and python_version < '4.0'",
             "version": "==5.8.0"
         },
         "lazy-object-proxy": {
@@ -114,7 +114,7 @@
                 "sha256:d65cc1df038ef55a99e617431f0553cd77763869eebdf9042403e16089fe746c",
                 "sha256:d7da2e1d5f558c37d6e8c1246f1aec1e7349e4913d8fb3cb289a35de573fe2eb"
             ],
-            "index": "pypi",
+            "markers": "python_version >= '3.5'",
             "version": "==0.812"
         },
         "mypy-extensions": {
@@ -145,9 +145,13 @@
                 "sha256:586d8fa9b1891f4b725f587ef267abe2a1bad89d6b184520c7f07a253dd6e217",
                 "sha256:f7e2072654a6b6afdf5e2fb38147d3e2d2d43c89f648637baab63e026481279b"
             ],
-            "index": "pypi",
+            "markers": "python_version ~= '3.6'",
             "version": "==2.8.2"
         },
+        "qemu": {
+            "editable": true,
+            "path": "."
+        },
         "toml": {
             "hashes": [
                 "sha256:806143ae5bfb6a3c6e736a764057db0e6a0e05e338b5630894a5f779cabb4f9b",
diff --git a/python/setup.cfg b/python/setup.cfg
index 3f07bd2752d..39dc135e601 100644
--- a/python/setup.cfg
+++ b/python/setup.cfg
@@ -22,6 +22,15 @@ packages =
     qemu.machine
     qemu.utils
 
+[options.extras_require]
+# Run `pipenv lock --dev` when changing these requirements.
+devel =
+    flake8 >= 3.6.0
+    isort >= 5.1.2
+    mypy >= 0.770
+    pylint >= 2.8.0
+
+
 [flake8]
 extend-ignore = E722  # Prefer pylint's bare-except checks to flake8's
 exclude = __pycache__,
-- 
2.31.1