...
BOM Coordinates: com.google.cloud:libraries-bom:2.7.1
...
Could not resolve version conflict among 
[
  io.grpc:grpc-alts:jar:1.24.1 -> io.grpc:grpc-core:jar:[1.24.1,1.24.1], 
  io.grpc:grpc-core:jar:1.24.1, 
  io.grpc:grpc-grpclb:jar:1.24.1 -> io.grpc:grpc-core:jar:[1.24.1,1.24.1], 
  io.grpc:grpc-netty:jar:1.24.1 -> io.grpc:grpc-core:jar:[1.24.1,1.24.1], 
  io.grpc:grpc-netty-shaded:jar:1.24.1 -> io.grpc:grpc-core:jar:[1.24.1,1.24.1], 
  io.grpc:grpc-okhttp:jar:1.24.1 -> io.grpc:grpc-core:jar:[1.24.1,1.24.1], 
  io.grpc:grpc-testing:jar:1.24.1 -> io.grpc:grpc-core:jar:[1.24.1,1.24.1], 
  com.google.cloud:google-cloud-bigtable:jar:1.6.0 -> io.grpc:grpc-core:jar:1.24.1, 
  com.google.cloud:google-cloud-datastore:jar:1.98.1-SNAPSHOT -> io.grpc:grpc-core:jar:1.24.1, 
  com.google.cloud:google-cloud-firestore:jar:1.28.1-SNAPSHOT -> io.grpc:grpc-core:jar:1.24.1, 
  com.google.cloud:google-cloud-firestore:jar:1.28.1-SNAPSHOT -> io.opencensus:opencensus-contrib-grpc-util:jar:0.24.0 -> io.grpc:grpc-core:jar:1.22.1, 
  io.grpc:grpc-all:jar:1.24.0 -> io.grpc:grpc-core:jar:[1.24.0,1.24.0],
  io.grpc:grpc-benchmarks:jar:1.24.0 -> io.grpc:grpc-core:jar:[1.24.0,1.24.0], 
  io.grpc:grpc-interop-testing:jar:1.24.0 -> io.grpc:grpc-core:jar:[1.24.0,1.24.0], 
  io.grpc:grpc-services:jar:1.24.0 -> io.grpc:grpc-core:jar:[1.24.0,1.24.0], 
  com.google.cloud:google-cloud-core-grpc:jar:1.91.3 -> io.grpc:grpc-core:jar:1.24.1
]