Fix pytest issues in Guix.

Key here was removing pytest-xdist from setup.py's "install_requires" list.
Otherwise running the test suite under Guix would fail with something like:

pkg_resources.ContextualVersionConflict: (pytest 5.3.5 (/gnu/store/9clwgf5svincpw3fbjcijdlw9mylyzn3-profile/lib/python3.8/site-packages), Requirement.parse('pytest>=6.0.0'), {'pytest-xdist'})

1 files changed, 5 insertions, 2 deletions

diff --git a/setup.py b/setup.py
index 1b1b9870..9decc2c1 100644
--- a/setup.py
+++ b/setup.py
@@ -43,8 +43,6 @@ install_requires = [
     # WTForms removed the "ext" module in 3.0.
     'wtforms>2.1,<3.0',
     'py-bcrypt',
-    'pytest>=2.3.1',
-    'pytest-xdist',
     'werkzeug>=0.7',
     # Celery 4.3.0 drops the "sqlite" transport alias making our tests fail.
     'celery>=3.0,<4.3.0',
@@ -80,6 +78,11 @@ install_requires = [
     # 'Pillow',
 ]
 
+extras_require = [
+    'pytest>=2.3.1',
+    'pytest-xdist',
+]
+
 with open(READMEFILE, encoding="utf-8") as fobj:
     long_description = fobj.read()