heroku node deployment(react-boilerplate) sh: 1: node-pre-gyp: not found error

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I'm getting error when deploying react-boilerplate on heroku with feathers, nodejs, mongodb, react. I specified up to date versions in package.json, and tried building with both npm and yarn but both fail. I appreciate your help!

"engines": {
"npm": ">=6.4.1",
"node": ">=v8.12.0",
"yarn": ">=1.10.1"
},

trial 1:
install with npm. error: sh: 1: node-pre-gyp: not found

NPM_CONFIG_LOGLEVEL=error
NPM_CONFIG_PRODUCTION=true
YARN_PRODUCTION=false
NODE_VERBOSE=false
NODE_ENV=production
NODE_MODULES_CACHE=true

-----> Installing binaries
engines.node (package.json): >=v8.12.0
engines.npm (package.json): >=6.4.1

Resolving node version >=v8.12.0...
Downloading and installing node 10.12.0...
Bootstrapping npm >=6.4.1 (replacing 6.4.1)...
npm >=6.4.1 installed
Resolving yarn version >=1.10.1...
Downloading and installing yarn (1.12.0)...
Installed yarn 1.12.0

> grpc@1.15.1 install /tmp/build_e7799f363b624e57eda6680a757c4fd4/node_modules/grpc
> node-pre-gyp install --fallback-to-build --library=static_library

sh: 1: node-pre-gyp: not found
npm ERR! file sh
npm ERR! code ELIFECYCLE
npm ERR! errno ENOENT
npm ERR! syscall spawn
npm ERR! grpc@1.15.1 install: `node-pre-gyp install --fallback-to-build --library=static_library`
npm ERR! spawn ENOENT
npm ERR!
npm ERR! Failed at the grpc@1.15.1 install script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

trial 2:
install with yarn. error: Error: spawn webpack ENOENT

NPM_CONFIG_LOGLEVEL=error
YARN_PRODUCTION=true
NODE_VERBOSE=false
NODE_ENV=production
NODE_MODULES_CACHE=true

-----> Installing binaries
engines.node (package.json): >=v8.12.0
engines.npm (package.json): >=6.4.1
engines.yarn (package.json): >=1.10.1

Resolving node version >=v8.12.0...
Downloading and installing node 10.12.0...
Bootstrapping npm >=6.4.1 (replacing 6.4.1)...
npm >=6.4.1 installed
Resolving yarn version >=1.10.1...
Downloading and installing yarn (1.12.0)...
Installed yarn 1.12.0


> seunghunlee-software@3.6.0 build /tmp/build_edb00e4a7279e6636f35f9ea79a9d0f8
> cross-env NODE_ENV=production webpack --config internals/webpack/webpack.prod.babel.js --color -p --progress --hide-modules --display-optimization-bailout

events.js:167
throw er; // Unhandled 'error' event
^
Error: spawn webpack ENOENT
at Process.ChildProcess._handle.onexit (internal/child_process.js:232:19)
at onErrorNT (internal/child_process.js:407:16)
at process._tickCallback (internal/process/next_tick.js:63:19)
at Function.Module.runMain (internal/modules/cjs/loader.js:744:11)
at startup (internal/bootstrap/node.js:285:19)
at bootstrapNodeJSCore (internal/bootstrap/node.js:739:3)
Emitted 'error' event at:
at Process.ChildProcess._handle.onexit (internal/child_process.js:238:12)
at onErrorNT (internal/child_process.js:407:16)
[... lines matching original stack trace ...]
at bootstrapNodeJSCore (internal/bootstrap/node.js:739:3)

Start by reproducing the Heroku deployment using the reported package.json engine settings and compare the npm and Yarn logs. Investigate the grpc install command reporting node-pre-gyp as missing and the production build reporting webpack as missing. Done means the deployment completes successfully with the supported dependency installation path.

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