+
+def ca_certs_path(fallback=httplib2.CA_CERTS):
+ """Return the path of the best available CA certs source.
+
+ This function searches for various distribution sources of CA
+ certificates, and returns the first it finds. If it doesn't find any,
+ it returns the value of `fallback` (httplib2's CA certs by default).
+ """
+ for ca_certs_path in [
+ # Arvados specific:
+ '/etc/arvados/ca-certificates.crt',
+ # Debian:
+ '/etc/ssl/certs/ca-certificates.crt',
+ # Red Hat:
+ '/etc/pki/tls/certs/ca-bundle.crt',
+ ]:
+ if os.path.exists(ca_certs_path):
+ return ca_certs_path
+ return fallback
+
+def new_request_id():
+ rid = "req-"
+ # 2**104 > 36**20 > 2**103
+ n = random.getrandbits(104)
+ for _ in range(20):
+ c = n % 36
+ if c < 10:
+ rid += chr(c+ord('0'))
+ else:
+ rid += chr(c+ord('a')-10)
+ n = n // 36
+ return rid