Add tools/lib/test_script.py w/get_provisioning_status().

tools/lib/test_script.py

@@ -0,0 +1,68 @@
+from __future__ import absolute_import
+from __future__ import print_function
+
+from typing import Tuple
+
+import os
+from version import PROVISION_VERSION
+
+def get_major_version(v):
+    # type: (str) -> int
+    return int(v.split('.')[0])
+
+def get_version_file():
+    # type: () -> str
+    return 'var/provision_version'
+
+PREAMBLE = '''
+Before we run tests, we make sure your provisioning version
+is correct by looking at var/provision_version, which is at
+version %s, and we compare it to the version in source
+control (version.py), which is %s.
+'''
+
+def preamble(version):
+    # type: (str) -> str
+    text = PREAMBLE % (version, PROVISION_VERSION)
+    text += '\n'
+    return text
+
+NEED_TO_DOWNGRADE = '''
+It looks like you checked out a branch that expects an older
+version of dependencies than the version you provisioned last.
+This may be ok, but it's likely that you either want to rebase
+your branch on top of upstream/master or re-provision your VM.
+'''
+
+NEED_TO_UPGRADE = '''
+It looks like you checked out a branch that has added
+dependencies beyond what you last provisioned.  Your tests
+are likely to fail until you add dependencies by provisioning.
+'''
+
+def get_provisioning_status():
+    # type: () -> Tuple[bool, str]
+
+    version_file = get_version_file()
+    if not os.path.exists(version_file):
+        # If the developer doesn't have a version_file written by
+        # a previous provision, then we don't do any safety checks
+        # here on the assumption that the developer is managing
+        # their own dependencies and not running provision.py.
+        return True, None
+
+    version = open(version_file).read().strip()
+
+    # Normal path for people that provision--we're all good!
+    if version == PROVISION_VERSION:
+        return True, None
+
+    # We may be more provisioned than the branch we just moved to.  As
+    # long as the major version hasn't changed, then we should be ok.
+    if version > PROVISION_VERSION:
+        if get_major_version(version) == get_major_version(PROVISION_VERSION):
+            return True, None
+        else:
+            return False, preamble(version) + NEED_TO_DOWNGRADE
+
+    return False, preamble(version) + NEED_TO_UPGRADE