python: Use and refer to the venv module rather than virtualenv

Using some form of sandbox with Python modules is a long standing best
practice with the language. There are a number of ways to have a Python
sandbox be created. At this point in time, it seems the Python community
is moving towards using the "venv" module provided with Python rather
than a separate tool. To match that we make the following changes:

- Refer to a "Python sandbox" rather than virtualenv in comments, etc.
- Install the python3-venv module in our container and not virtualenv.
- In our CI files, invoke "python -m venv" rather than "virtualenv".
- In documentation, tell users to install python3-venv and not
  virtualenv.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/tools/buildman/test.py b/tools/buildman/test.py
index c5feb74..e31e6c7 100644
--- a/tools/buildman/test.py
+++ b/tools/buildman/test.py
@@ -987,7 +987,7 @@
         diff = self.call_make_environment(tchn, full_path=True)[0]
         self.assertEqual({b'LC_ALL': b'C'}, diff)
 
-        # Test that virtualenv is handled correctly
+        # Test that Python sandbox is handled correctly
         tchn.override_toolchain = False
         sys.prefix = '/some/venv'
         env = dict(os.environb)
diff --git a/tools/buildman/toolchain.py b/tools/buildman/toolchain.py
index f4c832b..5e5bb4b 100644
--- a/tools/buildman/toolchain.py
+++ b/tools/buildman/toolchain.py
@@ -217,7 +217,7 @@
         elif self.cross:
             env[b'CROSS_COMPILE'] = tools.to_bytes(wrapper + self.cross)
 
-            # Detect a Python virtualenv and avoid defeating it
+            # Detect a Python sandbox and avoid defeating it
             if sys.prefix != sys.base_prefix:
                 paths = env[b'PATH'].split(b':')
                 new_paths = []
diff --git a/tools/docker/Dockerfile b/tools/docker/Dockerfile
index a0fd174..dec1d51 100644
--- a/tools/docker/Dockerfile
+++ b/tools/docker/Dockerfile
@@ -124,7 +124,7 @@
 	python3-dev \
 	python3-pip \
 	python3-sphinx \
-	python3-virtualenv \
+	python3-venv \
 	rpm2cpio \
 	sbsigntool \
 	socat \
@@ -136,7 +136,6 @@
 	texinfo \
 	util-linux \
 	uuid-dev \
-	virtualenv \
 	vboot-kernel-utils \
 	vboot-utils \
 	xilinx-bootgen \
@@ -313,7 +312,7 @@
 RUN wget -O /tmp/buildman-requirements.txt https://source.denx.de/u-boot/u-boot/-/raw/master/tools/buildman/requirements.txt
 RUN wget -O /tmp/patman-requirements.txt https://source.denx.de/u-boot/u-boot/-/raw/master/tools/patman/requirements.txt
 RUN wget -O /tmp/u_boot_pylib-requirements.txt https://source.denx.de/u-boot/u-boot/-/raw/master/tools/u_boot_pylib/requirements.txt
-RUN virtualenv -p /usr/bin/python3 /tmp/venv && \
+RUN python3 -m venv /tmp/venv && \
 	. /tmp/venv/bin/activate && \
 	pip install -r /tmp/pytest-requirements.txt \
 		-r /tmp/sphinx-requirements.txt \
diff --git a/tools/u_boot_pylib/test_util.py b/tools/u_boot_pylib/test_util.py
index 4835847..637403f 100644
--- a/tools/u_boot_pylib/test_util.py
+++ b/tools/u_boot_pylib/test_util.py
@@ -64,7 +64,7 @@
     if build_dir:
         prefix = 'PYTHONPATH=$PYTHONPATH:%s/sandbox_spl/tools ' % build_dir
 
-    # Detect a Python virtualenv and use 'coverage' instead
+    # Detect a Python sandbox and use 'coverage' instead
     covtool = ('python3-coverage' if sys.prefix == sys.base_prefix else
                'coverage')