Update minio/plex/nextcloud migrations to read from a file

test/minio/1.0.1/migrations/migrate

 #!/usr/bin/python3
 import json
+import os
 import sys
 
 
@@ -19,4 +20,6 @@ if __name__ == '__main__':
     if len(sys.argv) != 2:
         exit(1)
 
-    print(json.dumps(migrate(json.loads(sys.argv[1]))))
+    if os.path.exists(sys.argv[1]):
+        with open(sys.argv[1], 'r') as f:
+            print(json.dumps(migrate(json.loads(f.read()))))

test/nextcloud/1.1.0/migrations/migrate

 #!/usr/bin/python3
 import json
+import os
 import sys
 
 
@@ -20,4 +21,6 @@ if __name__ == '__main__':
     if len(sys.argv) != 2:
         exit(1)
 
-    print(json.dumps(migrate(json.loads(sys.argv[1]))))
+    if os.path.exists(sys.argv[1]):
+        with open(sys.argv[1], 'r') as f:
+            print(json.dumps(migrate(json.loads(f.read()))))

test/plex/1.0.1/migrations/migrate

 #!/usr/bin/python3
 import json
+import os
 import sys
 
 
@@ -28,4 +29,6 @@ if __name__ == '__main__':
     if len(sys.argv) != 2:
         exit(1)
 
-    print(json.dumps(migrate(json.loads(sys.argv[1]))))
+    if os.path.exists(sys.argv[1]):
+        with open(sys.argv[1], 'r') as f:
+            print(json.dumps(migrate(json.loads(f.read()))))