I have created test cases for verifying the bug. please execute these test cases once the fix is done.

Test case id: OPNST_ glance Bug:1534052_Internal Server Error returned, if delete image tag_1
Metric: 30 minutes
Test purpose: Verify that: Suppose an image is having 2 tags with same string , but different cases ( upper case and lower case “ABC” and “abc”), user should be able to delete just one of them( e.g. “ABC”);while keeping the other one( “abc”)
Configuration: An OpenStack environment with at least one controller (with keystone, glance), one compute node and one network node installed.
Test tool: tempest
References:
Applicability: if there are 2 tags, which are same string if ignore case, the issue exist
Pre-test conditions: OpenStack should be installed and all the services up and running 
Step Description: 
1.	create an image, with 2 tag( same string but different case – e.g. lower case and upper case ) "ABC" and "abc" 
2.	list the images glance image-show 
3.	delete tag with upper case “ABC” tag: glance image-tag-delete 
4.	list the image 
Result:
1.	User should be able to create the image with tag ABC and abc 
2.	User should able to list the image 
3.	User should be delete “ABC” tag without any error 
4.	User should be able to list the image with only “abc” tag (Lower case). The deleted tag ( Upper case ABC) should not be listed
Test verdict: TC pass only if user can delete the image tag without any error else TC failed
Test case id: OPNST_ glance Bug:1534052_Internal Server Error returned, if delete image tag_2
Metric: 30 minutes
Test purpose: Verify that: Suppose an image is having 2 tags with same string , but different cases ( upper case and lower case “ABC” and “abc”), user should be able to delete just one of them( e.g. “abc”);while keeping the other one( “ABC”).
Configuration: An OpenStack environment with at least one controller (with keystone, glance), one compute node and one network node installed.
Test tool: tempest
References:
Applicability: if there are 2 tags, which are same string if ignore case, the issue exist
Pre-test conditions: OpenStack should be installed and Rally should be installed in the server
Step Description: 
1.	create an image, with 2 tag( same string but different case – e.g. lower case and upper case ) "ABC" and "abc" 
2.	list the images glance image-show 
3.	delete tag with lower case “abc”: glance image-tag-delete 
4.	list the image 
Result:
1.	User should be able to create the image with tag ABC and abc 
2.	User should able to list the image 
3.	User should be delete “abc” tag without any error 
4.	User should be able to list the image with only “ABC” tag (Upper case). The deleted tag ( Lower case ABC) should not be listed
Test verdict: TC pass only if user can delete the image tag without any error else TC failed
Test case id: OPNST_ glance Bug:1534052_ Internal Server Error returned, if delete image tag_3
Metric: 30 minutes
Test purpose: Verify that: Suppose an image is having 2 tags with one of the being substring of other and also differ in cases ( upper case and lower case “ABCD” and “abc”), user should be able to delete just one of them( e.g. “ABCD”);while keeping the other one( “abc”).
Configuration: An OpenStack environment with at least one controller (with keystone, glance), one compute node and one network node installed.
Test tool: tempest
References:
Applicability: if there are 2 tags, which are same string if ignore case, the issue exist
Pre-test conditions: OpenStack should be installed 
Step Description: 
1.	create an image, with 2 tag( one of them as substring of other and also different cases – e.g. lower case and upper case ) "ABC" and "abc" 
2.	list the images glance image-show 
3.	delete “abc ”tag: glance image-tag-delete 
4.	restart the glance API 
5.	list the image 
Result:
1.	User should be able to create the image with tag ABC and abc 
2.	User should able to list the image 
3.	User should be delete “ABCD” tag without any error 
4.	User should be able to restart the glance API 
5.	User should be able to list the image with “ABCD” tag and the deleted tag should not be listed.
Test verdict: TC pass only if user can delete the image tag without any error else TC failed