Revert "tests: Use separate virtual environment for avocado"

This reverts commit e8e4298fea.

ensuregroup allows to specify both the acceptable versions of avocado,
and a locked version to be used when avocado is not installed as a system
pacakge.  This lets us install avocado in pyvenv/ using "mkvenv.py" and
reuse the distro package on Fedora and CentOS Stream (the only distros
where it's available).

ensuregroup's usage of "(>=..., <=...)" constraints when evaluating
the distro package, and "==" constraints when installing it from PyPI,
makes it possible to avoid conflicts between the known-good version and
a package plugins included in the distro.

This is because package plugins have "==" constraints on the version
that is included in the distro, and, using "pip install avocado==88.1"
on a venv that includes system packages will result in an error:

   avocado-framework-plugin-varianter-yaml-to-mux 98.0 requires avocado-framework==98.0, but you have avocado-framework 88.1 which is incompatible.
   avocado-framework-plugin-result-html 98.0 requires avocado-framework==98.0, but you have avocado-framework 88.1 which is incompatible.

But at the same time, if the venv does not include a system distribution
of avocado then we can install a known-good version and stick to LTS
releases.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1663
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tests/Makefile.include

@@ -89,10 +89,8 @@ distclean-tcg: $(DISTCLEAN_TCG_TARGET_RULES)
 # Build up our target list from the filtered list of ninja targets
 TARGETS=$(patsubst libqemu-%.fa, %, $(filter libqemu-%.fa, $(ninja-targets)))
 
-TESTS_VENV_DIR=$(BUILD_DIR)/tests/venv
-TESTS_VENV_REQ=$(SRC_PATH)/tests/requirements.txt
+TESTS_VENV_TOKEN=$(BUILD_DIR)/pyvenv/tests.group
 TESTS_RESULTS_DIR=$(BUILD_DIR)/tests/results
-TESTS_PYTHON=$(TESTS_VENV_DIR)/bin/python3
 ifndef AVOCADO_TESTS
 	AVOCADO_TESTS=tests/avocado
 endif
@@ -108,20 +106,19 @@ else
 endif
 
 quiet-venv-pip = $(quiet-@)$(call quiet-command-run, \
-    $(TESTS_PYTHON) -m pip -q --disable-pip-version-check $1, \
+    $(PYTHON) -m pip -q --disable-pip-version-check $1, \
     "VENVPIP","$1")
 
-$(TESTS_VENV_DIR): $(TESTS_VENV_REQ)
-	$(call quiet-command, $(PYTHON) -m venv $@, VENV, $@)
+$(TESTS_VENV_TOKEN): $(SRC_PATH)/pythondeps.toml
 	$(call quiet-venv-pip,install -e "$(SRC_PATH)/python/")
-	$(call quiet-venv-pip,install -r $(TESTS_VENV_REQ))
+	$(PYTHON) python/scripts/mkvenv.py ensuregroup --online $< avocado
 	$(call quiet-command, touch $@)
 
 $(TESTS_RESULTS_DIR):
 	$(call quiet-command, mkdir -p $@, \
             MKDIR, $@)
 
-check-venv: $(TESTS_VENV_DIR)
+check-venv: $(TESTS_VENV_TOKEN)
 
 FEDORA_31_ARCHES_TARGETS=$(patsubst %-softmmu,%, $(filter %-softmmu,$(TARGETS)))
 FEDORA_31_ARCHES_CANDIDATES=$(patsubst ppc64,ppc64le,$(FEDORA_31_ARCHES_TARGETS))
@@ -131,7 +128,7 @@ FEDORA_31_DOWNLOAD=$(filter $(FEDORA_31_ARCHES),$(FEDORA_31_ARCHES_CANDIDATES))
 # download one specific Fedora 31 image
 get-vm-image-fedora-31-%: check-venv
 	$(call quiet-command, \
-             $(TESTS_PYTHON) -m avocado vmimage get \
+             $(PYTHON) -m avocado vmimage get \
              --distro=fedora --distro-version=31 --arch=$*, \
 	"AVOCADO", "Downloading avocado tests VM image for $*")
 
@@ -140,7 +137,7 @@ get-vm-images: check-venv $(patsubst %,get-vm-image-fedora-31-%, $(FEDORA_31_DOW
 
 check-avocado: check-venv $(TESTS_RESULTS_DIR) get-vm-images
 	$(call quiet-command, \
-            $(TESTS_PYTHON) -m avocado \
+            $(PYTHON) -m avocado \
             --show=$(AVOCADO_SHOW) run --job-results-dir=$(TESTS_RESULTS_DIR) \
             $(if $(AVOCADO_TAGS),, --filter-by-tags-include-empty \
 			--filter-by-tags-include-empty-key) \
@@ -163,7 +160,7 @@ check:
 check-build: run-ninja
 
 check-clean:
-	rm -rf $(TESTS_VENV_DIR) $(TESTS_RESULTS_DIR)
+	rm -rf $(TESTS_RESULTS_DIR)
 
 clean: check-clean clean-tcg
 distclean: distclean-tcg

tests/requirements.txt

@@ -1,6 +0,0 @@
-# Add Python module requirements, one per line, to be installed
-# in the tests/venv Python virtual environment. For more info,
-# refer to: https://pip.pypa.io/en/stable/user_guide/#id1
-# Note that qemu.git/python/ is always implicitly installed.
-avocado-framework==88.1
-pycdlib==1.11.0

tests/vm/Makefile.include

@@ -5,7 +5,7 @@ ifeq ($(realpath $(SRC_PATH)),$(realpath .))
 VM_PYTHON = PYTHONPATH=$(SRC_PATH)/python /usr/bin/env python3
 VM_VENV =
 else
-VM_PYTHON = $(TESTS_PYTHON)
+VM_PYTHON = $(PYTHON)
 VM_VENV = check-venv
 endif