Replace md5 with oslo version

md5 is not an approved algorithm in FIPS mode, and trying to
instantiate a hashlib.md5() will fail when the system is running in
FIPS mode.

md5 is allowed when in a non-security context.  There is a plan to
add a keyword parameter (usedforsecurity) to hashlib.md5() to annotate
whether or not the instance is being used in a security context.

In the case where it is not, the instantiation of md5 will be allowed.
See https://bugs.python.org/issue9216 for more details.

Some downstream python versions already support this parameter.  To
support these versions, a new encapsulation of md5() has been added to
oslo_utils.  See https://review.opendev.org/#/c/750031/

This patch is to replace the instances of hashlib.md5() with this new
encapsulation, adding an annotation indicating whether the usage is
a security context or not.

In this case, we use md5 in a single case, when creating an identifier
for a mount point.

Change-Id: I08226895818185337425ebffc2464db05f3969c9
Depends-On: https://review.opendev.org/#/c/760160

lower-constraints.txt

@@ -37,7 +37,7 @@ oslo.log==3.44.0
 oslo.privsep==1.32.0
 oslo.serialization==2.29.0
 oslo.service==1.24.0
-oslo.utils==3.34.0
+oslo.utils==4.7.0
 oslo.vmware==2.17.0
 oslotest==3.2.0
 Paste==2.0.2

os_brick/remotefs/remotefs.py

@@ -15,13 +15,13 @@
 
 """Remote filesystem client utilities."""
 
-import hashlib
 import os
 import re
 import tempfile
 
 from oslo_concurrency import processutils
 from oslo_log import log as logging
+from oslo_utils.secretutils import md5
 import six
 
 from os_brick import exception
@@ -70,7 +70,8 @@ class RemoteFsClient(executor.Executor):
         """Return a string that represents hash of base_str (hex format)."""
         if isinstance(base_str, six.text_type):
             base_str = base_str.encode('utf-8')
-        return hashlib.md5(base_str).hexdigest()
+        return md5(base_str,
+                   usedforsecurity=False).hexdigest()
 
     def get_mount_point(self, device_name):
         """Get Mount Point.

requirements.txt

@@ -11,7 +11,7 @@ oslo.i18n>=3.24.0 # Apache-2.0
 oslo.privsep>=1.32.0 # Apache-2.0
 oslo.serialization>=2.29.0 # Apache-2.0
 oslo.service!=1.28.1,>=1.24.0 # Apache-2.0
-oslo.utils>=3.34.0 # Apache-2.0
+oslo.utils>=4.7.0 # Apache-2.0
 requests>=2.14.2 # Apache-2.0
 six>=1.10.0 # MIT
 tenacity>=6.0.0 # Apache-2.0