Default to normal severity when unspecified by advisory

Code Climate expects the severity to be one of the following values:
"critical", "normal", or "info". This commit defaults the severity to "normal"
when unspecified by the vulnerability advisory.

Author: dblandin

lib/cc/engine/bundler_audit/unpatched_gem_issue.rb

@@ -67,7 +67,7 @@ def remediation_points
         end
 
         def severity
-          SEVERITIES[advisory.criticality]
+          SEVERITIES.fetch(advisory.criticality, "normal")
         end
 
         def solution

spec/fixtures/unpatched_versions/issues.json

@@ -16,7 +16,7 @@
             "path": "Gemfile.lock"
         },
         "remediation_points": 50000,
-        "severity": null,
+        "severity": "normal",
         "type": "Issue"
     },
     {
@@ -36,7 +36,7 @@
             "path": "Gemfile.lock"
         },
         "remediation_points": 50000,
-        "severity": null,
+        "severity": "normal",
         "type": "Issue"
     },
     {
@@ -56,7 +56,7 @@
             "path": "Gemfile.lock"
         },
         "remediation_points": 50000,
-        "severity": null,
+        "severity": "normal",
         "type": "Issue"
     },
     {
@@ -76,7 +76,7 @@
             "path": "Gemfile.lock"
         },
         "remediation_points": 50000,
-        "severity": null,
+        "severity": "normal",
         "type": "Issue"
     },
     {
@@ -96,7 +96,7 @@
             "path": "Gemfile.lock"
         },
         "remediation_points": 50000,
-        "severity": null,
+        "severity": "normal",
         "type": "Issue"
     },
     {
@@ -116,7 +116,7 @@
             "path": "Gemfile.lock"
         },
         "remediation_points": 50000,
-        "severity": null,
+        "severity": "normal",
         "type": "Issue"
     },
     {
@@ -136,7 +136,7 @@
             "path": "Gemfile.lock"
         },
         "remediation_points": 5000000,
-        "severity": null,
+        "severity": "normal",
         "type": "Issue"
     },
     {
@@ -196,7 +196,7 @@
             "path": "Gemfile.lock"
         },
         "remediation_points": 500000,
-        "severity": null,
+        "severity": "normal",
         "type": "Issue"
     },
     {
@@ -216,7 +216,7 @@
             "path": "Gemfile.lock"
         },
         "remediation_points": 500000,
-        "severity": null,
+        "severity": "normal",
         "type": "Issue"
     },
     {
@@ -236,7 +236,7 @@
             "path": "Gemfile.lock"
         },
         "remediation_points": 5000000,
-        "severity": null,
+        "severity": "normal",
         "type": "Issue"
     }
 ]