Cannot compile tokenizers on PowerPC 9 while installing transformers
## Environment info
<!-- You can run the command `transformers-cli env` and copy-and-paste its output below.
     Don't forget to fill out the missing fields in that output! -->

- `transformers` version: 3.4.0
- Platform: PowerPC 9
- Python version: 3.7.7
- PyTorch version (GPU?): 1.5 w/ GPU
- Tensorflow version (GPU?): n/a
- Using GPU in script?: yes
- Using distributed or parallel set-up in script?: no

### Who can help
<!-- Your issue will be replied to more quickly if you can figure out the right person to tag with @
 If you know how to use git blame, that is the easiest way, otherwise, here is a rough guide of **who to tag**.
 Please tag fewer than 3 people.

 albert, bert, GPT2, XLM: @LysandreJik
 tokenizers: @mfuntowicz
 Trainer: @sgugger
 Speed and Memory Benchmarks: @patrickvonplaten
 Model Cards: @julien-c
 TextGeneration: @TevenLeScao
 examples/distillation: @VictorSanh
 nlp datasets: [different repo](https://github.com/huggingface/nlp)
 rust tokenizers: [different repo](https://github.com/huggingface/tokenizers)
 Text Generation: @patrickvonplaten @TevenLeScao
 Blenderbot: @patrickvonplaten
 Bart: @patrickvonplaten
 Marian: @patrickvonplaten
 Pegasus: @patrickvonplaten
 mBART: @patrickvonplaten
 T5: @patrickvonplaten
 Longformer/Reformer: @patrickvonplaten
 TransfoXL/XLNet: @TevenLeScao
 RAG: @patrickvonplaten, @lhoestq
 FSMT: @stas00
 examples/seq2seq: @patil-suraj
 examples/bert-loses-patience: @JetRunner
 ray/raytune: @richardliaw @amogkam
 tensorflow: @jplu
 examples/token-classification: @stefan-it
 documentation: @sgugger
 -->

@mfuntowicz

## Information

I am trying to install `transformers==3.4.0` on an PowerPC 9 system. It's an IBM compute rig.

## To reproduce

Steps to reproduce the behavior:

1. Create new `conda` environment with python 3.7
2. Run `pip install transformers==3.4.0` (the version that I need)

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```
Compiling tokenizers v0.10.1 (/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/tokenizers-lib)
       Running `rustc --crate-name tokenizers --edition=2018 tokenizers-lib/src/lib.rs --error-format=json --json=diagnostic-rendered-ansi --crate-type lib --emit=dep-info,metadata,link -C opt-level=3 -Cembed-bitcode=no -C metadata=204c4d103d08e9e3 -C extra-filename=-204c4d103d08e9e3 --out-dir /tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps -L dependency=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps --extern clap=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/libclap-b8e428690762cf7e.rmeta --extern derive_builder=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/libderive_builder-247f4f57ff4bf4c7.so --extern esaxx_rs=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/libesaxx_rs-28ce6f8a8d31c937.rmeta --extern indicatif=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/libindicatif-280a1d33f346e384.rmeta --extern itertools=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/libitertools-759131012594af62.rmeta --extern lazy_static=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/liblazy_static-0f749853bc34e9e0.rmeta --extern log=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/liblog-12a018fba7f0b36d.rmeta --extern onig=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/libonig-3ca2736cdef653d2.rmeta --extern rand=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/librand-52622a6339ec540d.rmeta --extern rayon=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/librayon-f4508233e0c77565.rmeta --extern rayon_cond=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/librayon_cond-d89d0c7f0a1d1a11.rmeta --extern regex=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/libregex-dbb55ca763c16a0e.rmeta --extern regex_syntax=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/libregex_syntax-c7a8a1f28fe982ac.rmeta --extern serde=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/libserde-11e7f5f85ab52b72.rmeta --extern serde_json=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/libserde_json-477c52136da5fafe.rmeta --extern spm_precompiled=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/libspm_precompiled-39a90f21c16965ef.rmeta --extern unicode_normalization_alignments=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/libunicode_normalization_alignments-157a660dec7f1476.rmeta --extern unicode_segmentation=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/libunicode_segmentation-66856f91381ae1a4.rmeta --extern unicode_categories=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/libunicode_categories-209e6f430e5d88d1.rmeta -L native=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/build/esaxx-rs-62ba703c44f19ac6/out -L native=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/build/onig_sys-091ecfe4b66243c7/out`
  error[E0603]: module `export` is private
     --> tokenizers-lib/src/tokenizer/mod.rs:24:12
      |
  24  | use serde::export::Formatter;
      |            ^^^^^^ private module
      |
  note: the module `export` is defined here
     --> /home/mengk/.cargo/registry/src/github.com-1ecc6299db9ec823/serde-1.0.119/src/lib.rs:275:5
      |
  275 | use self::__private as export;
      |     ^^^^^^^^^^^^^^^^^^^^^^^^^
  
  error: aborting due to previous error
  
  For more information about this error, try `rustc --explain E0603`.
  error: could not compile `tokenizers`.
  
  Caused by:
    process didn't exit successfully: `rustc --crate-name tokenizers --edition=2018 tokenizers-lib/src/lib.rs --error-format=json --json=diagnostic-rendered-ansi --crate-type lib --emit=dep-info,metadata,link -C opt-level=3 -Cembed-bitcode=no -C metadata=204c4d103d08e9e3 -C extra-filename=-204c4d103d08e9e3 --out-dir /tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps -L dependency=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps --extern clap=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/libclap-b8e428690762cf7e.rmeta --extern derive_builder=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/libderive_builder-247f4f57ff4bf4c7.so --extern esaxx_rs=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/libesaxx_rs-28ce6f8a8d31c937.rmeta --extern indicatif=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/libindicatif-280a1d33f346e384.rmeta --extern itertools=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/libitertools-759131012594af62.rmeta --extern lazy_static=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/liblazy_static-0f749853bc34e9e0.rmeta --extern log=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/liblog-12a018fba7f0b36d.rmeta --extern onig=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/libonig-3ca2736cdef653d2.rmeta --extern rand=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/librand-52622a6339ec540d.rmeta --extern rayon=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/librayon-f4508233e0c77565.rmeta --extern rayon_cond=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/librayon_cond-d89d0c7f0a1d1a11.rmeta --extern regex=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/libregex-dbb55ca763c16a0e.rmeta --extern regex_syntax=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/libregex_syntax-c7a8a1f28fe982ac.rmeta --extern serde=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/libserde-11e7f5f85ab52b72.rmeta --extern serde_json=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/libserde_json-477c52136da5fafe.rmeta --extern spm_precompiled=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/libspm_precompiled-39a90f21c16965ef.rmeta --extern unicode_normalization_alignments=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/libunicode_normalization_alignments-157a660dec7f1476.rmeta --extern unicode_segmentation=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/libunicode_segmentation-66856f91381ae1a4.rmeta --extern unicode_categories=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/deps/libunicode_categories-209e6f430e5d88d1.rmeta -L native=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/build/esaxx-rs-62ba703c44f19ac6/out -L native=/tmp/pip-install-4jlvfd19/tokenizers_3c1b3bbe26064417aa8614a7fb564203/target/release/build/onig_sys-091ecfe4b66243c7/out` (exit code: 1)
  cargo rustc --lib --manifest-path Cargo.toml --features pyo3/extension-module --release --verbose -- --crate-type cdylib
  error: cargo failed with code: 101
  
  ----------------------------------------
  ERROR: Failed building wheel for tokenizers
Failed to build tokenizers
ERROR: Could not build wheels for tokenizers which use PEP 517 and cannot be installed directly
```

## Expected behavior

There shouldn't be any error messages.

Sidenote: before getting this, I had an error complaining that I didn't have rust installed, but I did so using the command given on the official website.

<!-- A clear and concise description of what you would expect to happen. -->

Hello! Could you open an issue on the [tokenizers](https://github.com/huggingface/tokenizers) repository instead? @n1t0 will probably know what's up!<|||||>Done! https://github.com/huggingface/tokenizers/issues/604<|||||>This is actually a transformers problem I think. It's the old versions of tokenizers imported using a path that has since become private. It's fixed in the newer versions, but transformers is still pinned to the old version: https://github.com/huggingface/transformers/issues/9649<|||||>Ah, installing something newer, e.g. `transformers==4.2.2`, has fixed it. Thanks so much!