How do I verify an SSL certificate in python?

I need to verify that a certificate was signed by my custom CA. Using OpenSSL command-line utilities this is easy to do:

# Custom CA file: ca-cert.pem
# Cert signed by above CA: bob.cert
$ openssl verify -CAfile test-ca-cert.pem bob.cert
bob.cert: OK

But I need to do the same thing in Python, and I really don't want to call out to command-line utilities. As far as I'm aware, M2Crypto is the "most complete" python wrapper for OpenSSL, but I can't figure out how to accomplish what the command-line utility does!

Referencing this question for how to accomplish this same task in C code, I've been able to get about half-way. The variable names I chose are the same ones used in the source code for the openssl verify command-line utility, see openssl-xxx/apps/verify.c.

import M2Crypto as m2
# Load the certificates
cacert = m2.X509.load_cert('test-ca-cert.pem')   # Create cert object from CA cert file
bobcert = m2.X509.load_cert('bob.cert')     # Create cert object from Bob's cert file
cert_ctx = m2.X509.X509_Store()             # Step 1 from referenced C code steps
csc = m2.X509.X509_Store_Context(cert_ctx)  # Step 2 & 5
cert_ctx.add_cert(cacert)                   # Step 3
cert_ctx.add_cert(bobcert)                  # ditto
# Skip step 4 (no CRLs to add)
# Step 5 is combined with step 2...I think. (X509_STORE_CTX_init: Python creates and 
#   initialises an object in the same step)
# Skip step 6? (can't find anything corresponding to 
#   X509_STORE_CTX_set_purpose, not sure if we need to anyway???)
# 
# It all falls apart at this point, as steps 7 and 8 don't have any corresponding
# functions in M2Crypto -- I even grepped the entire source code of M2Crypto, and
# neither of the following functions are present in it:
# Step 7: X509_STORE_CTX_set_cert - Tell the context which certificate to validate.
# Step 8: X509_verify_cert - Finally, validate it

So I'm halfway there, but I can't seem to actually get the validation done! Am I missing something? Is there some other function I should be using from M2Crypto? Should I be looking for a completely different python wrapper of OpenSSL? How can I accomplish this task in python!?!?

Note that I'm using certificates to encrypt/decrypt FILES, so I'm not interested in using the SSL-connection-based peer certificate verification (which has already been answered), because I don't have any SSL connections going.