ALL smoke.py invocations are done through smoke_command()

This function returns a string command with fully qualified paths to a
valid (>= 2.5) Python interpreter and to the smoke.py file.

SConscript.smoke

@@ -4,6 +4,7 @@
 # e.g.)
 
 import os
+from buildscripts import utils
 
 Import( "has_option env shellEnv testEnv" )
 
@@ -42,7 +43,8 @@ def addSmoketest( name, deps ):
         else:
             target = name[5].lower() + name[6:]
 
-    addTest(name, deps, [ "python buildscripts/smoke.py " + " ".join(smokeFlags) + ' ' + target ])
+    smokeArgs = smokeFlags + [target]
+    addTest(name, deps, utils.smoke_command(*smokeArgs))
 
 addSmoketest( "smoke", [ add_exe( "test" ), add_exe( "mongod" ), add_exe( "mongo" ) ] )
 addSmoketest( "smokePerf", [ add_exe("perftest") ]  )

buildscripts/utils.py

@@ -3,6 +3,10 @@
 import socket
 import time
 import os
+import os.path
+import itertools
+import subprocess
+import sys
 # various utilities that are handy
 
 def getAllSourceFiles( arr=None , prefix="." ):
@@ -134,3 +138,47 @@ def didMongodStart( port=27017 , timeout=20 ):
             timeout = timeout - 1
     return False
 
+def which(executable):
+    if sys.platform == 'win32':
+        paths = os.environ.get('Path', '').split(';')
+    else:
+        paths = os.environ.get('PATH', '').split(':')
+
+    for path in paths:
+        path = os.path.expandvars(path)
+        path = os.path.expanduser(path)
+        path = os.path.abspath(path)
+        executable_path = os.path.join(path, executable)
+        if os.path.exists(executable_path):
+            return executable_path
+
+    return executable
+
+def find_python(min_version=(2, 5)):
+    # if this script is being run by py2.5 or greater,
+    # then we assume that "python" points to a 2.5 or
+    # greater python VM. otherwise, explicitly use 2.5
+    # which we assume to be installed.
+    version = re.compile(r'[Pp]ython ([\d\.]+)', re.MULTILINE)
+    binaries = ('python27', 'python2.7', 'python26', 'python2.6', 'python25', 'python2.5', 'python')
+    for binary in binaries:
+        try:
+            out, err = subprocess.Popen([binary, '-V'], stdout=subprocess.PIPE, stderr=subprocess.PIPE).communicate()
+            for stream in (out, err):
+                match = version.search(stream)
+                if match:
+                    versiontuple = tuple(map(int, match.group(1).split('.')))
+                    if versiontuple >= (2, 5):
+                        return which(binary)
+        except:
+            pass
+
+    raise Exception('could not find suitable Python (version >= %s)' % '.'.join(min_version))
+
+def smoke_command(*args):
+    here = os.path.dirname(__file__)
+    smoke_py = os.path.join(here, 'smoke.py')
+    return ' '.join(itertools.chain(
+        (find_python(), smoke_py),
+        args))
+

src/mongo/SConscript

@@ -3,7 +3,7 @@
 # This SConscript describes build rules for the "mongo" project.
 
 import os
-import buildscripts.utils as utils
+from buildscripts import utils
 
 Import("env")
 Import("shellEnv")
@@ -551,7 +551,7 @@ def build_and_test_client(env, target, source):
 
     call(scons_command + ["libmongoclient.a", "clientTests"], cwd=installDir)
 
-    return bool(call(["python", "buildscripts/smoke.py",
-                      "--test-path", installDir, "client"]))
+    return bool(call(utils.smoke_command([
+                      "--test-path", installDir, "client"])))
 env.Alias("clientBuild", [mongod, '$INSTALL_DIR'], [build_and_test_client])
 env.AlwaysBuild("clientBuild")