install_venv: pip install M2Crypto doesn't work on Fedora

... so use the system m2crypto library instead.

M2Crypto won't build on Fedora because of some bizarre differences with
Fedora's OpenSSL headers. I can get it to build by doing e.g.

 $> python ./tools/install_venv.py
 $> cd .nova-venv/build/M2Crypto
 $> for i in SWIG/_ec.i SWIG/_evp.i; do sed -i -e "s/opensslconf/opensslconf-x86_64/" $i ; done
 $> cd -
 $> SWIG_FEATURES=-cpperraswarn ./tools/with_venv.sh pip install M2Crypto

but that's clearly no fun. It should be fine to just use the system
version.

Change-Id: I94c7464bf60ae586e16a2f38b7440cea8dc110e5

tools/install_venv.py

@@ -86,6 +86,9 @@ class Distro(object):
             ' requires virtualenv, please install it using your'
             ' favorite package management tool')
 
+    def install_m2crypto(self):
+        pip_install('M2Crypto')
+
 
 class Fedora(Distro):
 
@@ -105,6 +108,14 @@ class Fedora(Distro):
 
         super(Fedora, self).install_virtualenv()
 
+    #
+    # pip install M2Crypto fails on Fedora because of
+    # weird differences with OpenSSL headers
+    #
+    def install_m2crypto(self):
+        if not self.check_pkg('m2crypto'):
+            self.yum_install('m2crypto')
+
 
 def get_distro():
     if os.path.exists('/etc/fedora-release'):
@@ -145,6 +156,8 @@ def install_dependencies(venv=VENV):
 
     pip_install('-r', PIP_REQUIRES)
 
+    get_distro().install_m2crypto()
+
     # Tell the virtual env how to "import nova"
     pthfile = os.path.join(venv, "lib", PY_VERSION, "site-packages",
                         "nova.pth")