Raise a ParseError on dangling close curly brace #2819

Job	Run time
lint	1m 33s
system_tests	2m 11s
mongodb_test (gemfiles/mongoid_9.gemfile)	3m 13s
javascript_test	26s
mongodb_test (gemfiles/mongoid_8.gemfile)	3m 15s
test (Gemfile, 3.4)	3m 19s
postgres_test (gemfiles/rails_master.gemfile, 3.3, 1)	3m 12s
test (Gemfile, 2.7)	5m 4s
test (gemfiles/rails_7.0.gemfile, 3.1)	3m 28s
postgres_test (gemfiles/rails_7.1_postgresql.gemfile, 3.3)	3m 13s
test (gemfiles/rails_7.0.gemfile, 3.2)	3m 32s
test (gemfiles/rails_7.1.gemfile, 3.3)	3m 44s
test (gemfiles/rails_master.gemfile, 3.3, 1, 1, 1)	3m 51s
test (gemfiles/rails_master.gemfile, 3.4, 1, 1, 1)	3m 46s
	43m 47s

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