Add the version of pex used to build a pex to build_properties. (#687)

pex/pex_info.py

@@ -13,6 +13,7 @@
 from pex.orderedset import OrderedSet
 from pex.util import merge_split
 from pex.variables import ENV
+from pex.version import __version__ as pex_version
 
 
 # TODO(wickman) Split this into a PexInfoBuilder/PexInfo to ensure immutability.
@@ -56,6 +57,7 @@ def make_build_properties(cls, interpreter=None):
     plat = Platform.current()
     platform_name = plat.platform
     return {
+      'pex_version': pex_version,
       'class': pi.identity.interpreter,
       'version': pi.identity.version,
       'platform': platform_name,

tests/test_pex_info.py

@@ -9,6 +9,7 @@
 from pex.orderedset import OrderedSet
 from pex.pex_info import PexInfo
 from pex.variables import ENV, Variables
+from pex.version import __version__ as pex_version
 
 
 def make_pex_info(requirements):
@@ -75,3 +76,7 @@ def test_from_env():
               always_write_cache=True)
 
   assert_same_info(PexInfo(info=info), PexInfo.from_env(env=Variables(environ=environ)))
+
+
+def test_build_properties():
+  assert pex_version == PexInfo.default().build_properties['pex_version']