SERVER-28475 Require SCons 2.5 and Python 2.7

Also, a drive by for making the search path for SCons
in buildscripts/scons.py absolute, obviating the need to
explicitly load the "install" tool. This is effectively a partial
revert of the changes made for SERVER-28497.

SConstruct

@@ -20,7 +20,8 @@ import SCons
 # we are to avoid bulk loading all tools in the DefaultEnvironment.
 DefaultEnvironment(tools=[])
 
-EnsureSConsVersion( 2, 3, 5 )
+EnsurePythonVersion(2, 7)
+EnsureSConsVersion(2, 5)
 
 from buildscripts import utils
 from buildscripts import moduleconfig
@@ -587,11 +588,11 @@ def variable_arch_converter(val):
 def decide_platform_tools():
     if is_running_os('windows'):
         # we only support MS toolchain on windows
-        return ['msvc', 'mslink', 'mslib', 'masm', 'install']
+        return ['msvc', 'mslink', 'mslib', 'masm']
     elif is_running_os('linux', 'solaris'):
-        return ['gcc', 'g++', 'gnulink', 'ar', 'gas', 'install']
+        return ['gcc', 'g++', 'gnulink', 'ar', 'gas']
     elif is_running_os('darwin'):
-        return ['gcc', 'g++', 'applelink', 'ar', 'as', 'install']
+        return ['gcc', 'g++', 'applelink', 'ar', 'as']
     else:
         return ["default"]
 

buildscripts/scons.py

@@ -7,7 +7,7 @@
 
 SCONS_VERSION = os.environ.get('SCONS_VERSION', "2.5.0")
 
-mongodb_root = os.path.dirname(os.path.dirname(__file__))
+mongodb_root = os.path.abspath(os.path.dirname(os.path.dirname(__file__)))
 scons_dir = os.path.join(mongodb_root, 'src', 'third_party','scons-' + SCONS_VERSION,
                          'scons-local-' + SCONS_VERSION)