helm.bzl seems broken

[borg286]

I just tried to clone the istio helm example to see if rules_helm would work and it is failing to build.

mrmath@mrmath9055096 ~/rules_helm_example
 % bazel run  //charts/istio:istio_init.install
Starting local Bazel server and connecting to it...
DEBUG: Rule 'com_github_tmc_rules_helm' indicated that a canonical reproducible form can be obtained by modifying arguments commit = "0ed7e81ff002408d933d069662a337c5faeb1ce7", shallow_since = "1564769992 -0700" and dropping ["branch"]
DEBUG: Repository com_github_tmc_rules_helm instantiated at:
  /home/mrmath/rules_helm_example/WORKSPACE:4:15: in <toplevel>
Repository rule git_repository defined at:
  /home/mrmath/.cache/bazel/_bazel_mrmath/19d4dc9c1409e24dddaef30b2dcf417f/external/bazel_tools/tools/build_defs/repo/git.bzl:199:33: in <toplevel>
ERROR: /home/mrmath/.cache/bazel/_bazel_mrmath/19d4dc9c1409e24dddaef30b2dcf417f/external/com_github_tmc_rules_helm/helm/helm.bzl:11:14: invalid escape sequence: \$. Use '\\' to insert '\'.
ERROR: /home/mrmath/.cache/bazel/_bazel_mrmath/19d4dc9c1409e24dddaef30b2dcf417f/external/com_github_tmc_rules_helm/helm/helm.bzl:12:7: invalid escape sequence: \$. Use '\\' to insert '\'.
ERROR: /home/mrmath/.cache/bazel/_bazel_mrmath/19d4dc9c1409e24dddaef30b2dcf417f/external/com_github_tmc_rules_helm/helm/helm.bzl:12:19: invalid escape sequence: \$. Use '\\' to insert '\'.
ERROR: /home/mrmath/.cache/bazel/_bazel_mrmath/19d4dc9c1409e24dddaef30b2dcf417f/external/com_github_tmc_rules_helm/helm/helm.bzl:12:28: invalid escape sequence: \$. Use '\\' to insert '\'.
ERROR: /home/mrmath/.cache/bazel/_bazel_mrmath/19d4dc9c1409e24dddaef30b2dcf417f/external/com_github_tmc_rules_helm/helm/helm.bzl:112:12: invalid escape sequence: \$. Use '\\' to insert '\'.
ERROR: /home/mrmath/.cache/bazel/_bazel_mrmath/19d4dc9c1409e24dddaef30b2dcf417f/external/com_github_tmc_rules_helm/helm/helm.bzl:112:36: invalid escape sequence: \$. Use '\\' to insert '\'.
ERROR: /home/mrmath/.cache/bazel/_bazel_mrmath/19d4dc9c1409e24dddaef30b2dcf417f/external/com_github_tmc_rules_helm/helm/helm.bzl:113:12: invalid escape sequence: \$. Use '\\' to insert '\'.
ERROR: /home/mrmath/.cache/bazel/_bazel_mrmath/19d4dc9c1409e24dddaef30b2dcf417f/external/com_github_tmc_rules_helm/helm/helm.bzl:113:27: invalid escape sequence: \$. Use '\\' to insert '\'.
ERROR: /home/mrmath/.cache/bazel/_bazel_mrmath/19d4dc9c1409e24dddaef30b2dcf417f/external/com_github_tmc_rules_helm/helm/helm.bzl:114:8: invalid escape sequence: \$. Use '\\' to insert '\'.
ERROR: /home/mrmath/.cache/bazel/_bazel_mrmath/19d4dc9c1409e24dddaef30b2dcf417f/external/com_github_tmc_rules_helm/helm/helm.bzl:115:22: invalid escape sequence: \$. Use '\\' to insert '\'.
ERROR: /home/mrmath/.cache/bazel/_bazel_mrmath/19d4dc9c1409e24dddaef30b2dcf417f/external/com_github_tmc_rules_helm/helm/helm.bzl:115:36: invalid escape sequence: \$. Use '\\' to insert '\'.
ERROR: /home/mrmath/.cache/bazel/_bazel_mrmath/19d4dc9c1409e24dddaef30b2dcf417f/external/com_github_tmc_rules_helm/helm/helm.bzl:115:53: invalid escape sequence: \$. Use '\\' to insert '\'.
ERROR: /home/mrmath/.cache/bazel/_bazel_mrmath/19d4dc9c1409e24dddaef30b2dcf417f/external/com_github_tmc_rules_helm/helm/helm.bzl:115:124: invalid escape sequence: \$. Use '\\' to insert '\'.
ERROR: /home/mrmath/.cache/bazel/_bazel_mrmath/19d4dc9c1409e24dddaef30b2dcf417f/external/com_github_tmc_rules_helm/helm/helm.bzl:116:10: invalid escape sequence: \$. Use '\\' to insert '\'.
ERROR: /home/mrmath/.cache/bazel/_bazel_mrmath/19d4dc9c1409e24dddaef30b2dcf417f/external/com_github_tmc_rules_helm/helm/helm.bzl:117:22: invalid escape sequence: \$. Use '\\' to insert '\'.
ERROR: /home/mrmath/.cache/bazel/_bazel_mrmath/19d4dc9c1409e24dddaef30b2dcf417f/external/com_github_tmc_rules_helm/helm/helm.bzl:119:22: invalid escape sequence: \$. Use '\\' to insert '\'.
ERROR: /home/mrmath/.cache/bazel/_bazel_mrmath/19d4dc9c1409e24dddaef30b2dcf417f/external/com_github_tmc_rules_helm/helm/helm.bzl:119:36: invalid escape sequence: \$. Use '\\' to insert '\'.
ERROR: Skipping '//charts/istio:istio_init.install': error loading package 'charts/istio': compilation of module 'helm/helm.bzl' failed
WARNING: Target pattern parsing failed.
ERROR: error loading package 'charts/istio': compilation of module 'helm/helm.bzl' failed
INFO: Elapsed time: 2.967s
INFO: 0 processes.
FAILED: Build did NOT complete successfully (0 packages loaded)
FAILED: Build did NOT complete successfully (0 packages loaded)
    currently loading: charts/istio

I really don't understand what the author is trying to do in this bzl file, so I can't make a recommendation on the fix.