El Capital 以降の System Integrity Protection という仕組みのアレらしいので。
brew install する前は↓だったみたい (本当か？)
$ pip freeze altgraph==0.10.2 bdist-mpkg==0.5.0 bonjour-py==0.3 macholib==1.5.1 matplotlib==1.3.1 modulegraph==0.10.4 numpy==1.8.0rc1 py2app==0.7.3 pyobjc-core==2.5.1 pyobjc-framework-Accounts==2.5.1 pyobjc-framework-AddressBook==2.5.1 pyobjc-framework-AppleScriptKit==2.5.1 pyobjc-framework-AppleScriptObjC==2.5.1 pyobjc-framework-Automator==2.5.1 pyobjc-framework-CFNetwork==2.5.1 pyobjc-framework-Cocoa==2.5.1 pyobjc-framework-Collaboration==2.5.1 pyobjc-framework-CoreData==2.5.1 pyobjc-framework-CoreLocation==2.5.1 pyobjc-framework-CoreText==2.5.1 pyobjc-framework-DictionaryServices==2.5.1 pyobjc-framework-EventKit==2.5.1 pyobjc-framework-ExceptionHandling==2.5.1 pyobjc-framework-FSEvents==2.5.1 pyobjc-framework-InputMethodKit==2.5.1 pyobjc-framework-InstallerPlugins==2.5.1 pyobjc-framework-InstantMessage==2.5.1 pyobjc-framework-LatentSemanticMapping==2.5.1 pyobjc-framework-LaunchServices==2.5.1 pyobjc-framework-Message==2.5.1 pyobjc-framework-OpenDirectory==2.5.1 pyobjc-framework-PreferencePanes==2.5.1 pyobjc-framework-PubSub==2.5.1 pyobjc-framework-QTKit==2.5.1 pyobjc-framework-Quartz==2.5.1 pyobjc-framework-ScreenSaver==2.5.1 pyobjc-framework-ScriptingBridge==2.5.1 pyobjc-framework-SearchKit==2.5.1 pyobjc-framework-ServiceManagement==2.5.1 pyobjc-framework-Social==2.5.1 pyobjc-framework-SyncServices==2.5.1 pyobjc-framework-SystemConfiguration==2.5.1 pyobjc-framework-WebKit==2.5.1 pyOpenSSL==0.13.1 pyparsing==2.0.1 python-dateutil==1.5 pytz==2013.7 scipy==0.13.0b1 six==1.4.1 wheel==0.26.0 xattr==0.6.4 zope.interface==4.1.1
