Backtrace on series format

[freimer]

Describe the bug Receive backtrace on series type format string

To Reproduce Specify a format string of "%Y-%m-%d %H:%M:%S%Z"

1. Schema (if applicable)

   {
     "type": "series",
     "format": "%Y-%m-%d %H:%M:%S%Z",
     "incrementing": { "start": "2023-01-01 09:00:00", "increment": "1h" }
   }

2. See error

   
   thread 'main' panicked at 'a Display implementation returned an error unexpectedly: Error', /rustc/c5d82ed7a4ad94a538bb87e5016e7d5ce0bd434b/library/alloc/src/string.rs:2537:14
   stack backtrace:
   0: rust_begin_unwind
            at /rustc/c5d82ed7a4ad94a538bb87e5016e7d5ce0bd434b/library/std/src/panicking.rs:575:5
   1: core::panicking::panic_fmt
            at /rustc/c5d82ed7a4ad94a538bb87e5016e7d5ce0bd434b/library/core/src/panicking.rs:65:14
   2: core::result::unwrap_failed
            at /rustc/c5d82ed7a4ad94a538bb87e5016e7d5ce0bd434b/library/core/src/result.rs:1791:5
   3: <synth_core::graph::series::SeriesFormatter<S> as synth_gen::generator::Generator>::next
   4: <synth_gen::generator::try::TryOnce<G> as synth_gen::generator::Generator>::next
   5: <synth_core::graph::series::SeriesNode as synth_gen::generator::Generator>::next
   6: <synth_core::graph::Graph as synth_gen::generator::Generator>::next
   7: <synth_gen::generator::Concatenate<Left,Right> as synth_gen::generator::Generator>::next
   8: <synth_gen::generator::Concatenate<Left,Right> as synth_gen::generator::Generator>::next
   9: <synth_gen::generator::Chain<G> as synth_gen::generator::Generator>::next
   10: <synth_gen::generator::Brace<BG,G,EG> as synth_gen::generator::Generator>::next
   11: <synth_core::graph::object::ObjectNode as synth_gen::generator::Generator>::next
   12: <synth_core::graph::Graph as synth_gen::generator::Generator>::next
   13: <synth_gen::generator::Repeat<G> as synth_gen::generator::Generator>::next
   14: <synth_gen::generator::Brace<BG,G,EG> as synth_gen::generator::Generator>::next
   15: <synth_gen::generator::try::AndThenTry<TG,F,O> as synth_gen::generator::Generator>::next
   16: <synth_core::graph::Graph as synth_gen::generator::Generator>::next
   17: <synth_gen::generator::Concatenate<Left,Right> as synth_gen::generator::Generator>::next
   18: <synth_gen::generator::Chain<G> as synth_gen::generator::Generator>::next
   19: <synth_gen::generator::Brace<BG,G,EG> as synth_gen::generator::Generator>::next
   20: <synth_core::graph::object::ObjectNode as synth_gen::generator::Generator>::next
   21: <synth_core::graph::Graph as synth_gen::generator::Generator>::next
   22: synth_gen::generator::Generator::complete
   23: synth::sampler::Sampler::sample_seeded
   24: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
   25: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
   26: std::thread::local::LocalKey<T>::with
   27: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
   28: async_io::driver::block_on
   29: async_global_executor::executor::block_on
   30: std::thread::local::LocalKey<T>::with
   31: std::thread::local::LocalKey<T>::with
   32: async_std::task::builder::Builder::blocking
   33: synth::main

**Expected behavior**
That it would not panic and provide an appropriate error message.

**Screenshots**
Not necessary

**Environment (please complete the following information):**
 - OS: Linux
 - Version: Ubuntu 22.04

**Additional context**
Add any other context about the problem here.

[freimer]

It also throws errors, "input contains invalid characters" although not backtraces, simply by removing the dashes between %Y-%m-%d in the format string. Sorry, I have to move on to something else.